diff --git a/qa/pull-tester/rpc-tests.py b/qa/pull-tester/rpc-tests.py
index e3921cfbe..f65a3eefc 100755
--- a/qa/pull-tester/rpc-tests.py
+++ b/qa/pull-tester/rpc-tests.py
@@ -142,6 +142,7 @@ testScripts = [
     'segwit.py',
     'importprunedfunds.py',
     'signmessages.py',
+    'p2p-compactblocks.py',
 ]
 if ENABLE_ZMQ:
     testScripts.append('zmq_test.py')
diff --git a/qa/rpc-tests/p2p-compactblocks.py b/qa/rpc-tests/p2p-compactblocks.py
new file mode 100755
index 000000000..7fe7ecc16
--- /dev/null
+++ b/qa/rpc-tests/p2p-compactblocks.py
@@ -0,0 +1,608 @@
+#!/usr/bin/env python3
+# Copyright (c) 2016 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+from test_framework.mininode import *
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import *
+from test_framework.blocktools import create_block, create_coinbase
+from test_framework.siphash import siphash256
+from test_framework.script import CScript, OP_TRUE
+
+'''
+CompactBlocksTest -- test compact blocks (BIP 152)
+'''
+
+
+# TestNode: A peer we use to send messages to bitcoind, and store responses.
+class TestNode(SingleNodeConnCB):
+    def __init__(self):
+        SingleNodeConnCB.__init__(self)
+        self.last_sendcmpct = None
+        self.last_headers = None
+        self.last_inv = None
+        self.last_cmpctblock = None
+        self.block_announced = False
+        self.last_getdata = None
+        self.last_getblocktxn = None
+        self.last_block = None
+        self.last_blocktxn = None
+
+    def on_sendcmpct(self, conn, message):
+        self.last_sendcmpct = message
+
+    def on_block(self, conn, message):
+        self.last_block = message
+
+    def on_cmpctblock(self, conn, message):
+        self.last_cmpctblock = message
+        self.block_announced = True
+
+    def on_headers(self, conn, message):
+        self.last_headers = message
+        self.block_announced = True
+
+    def on_inv(self, conn, message):
+        self.last_inv = message
+        self.block_announced = True
+
+    def on_getdata(self, conn, message):
+        self.last_getdata = message
+
+    def on_getblocktxn(self, conn, message):
+        self.last_getblocktxn = message
+
+    def on_blocktxn(self, conn, message):
+        self.last_blocktxn = message
+
+    # Requires caller to hold mininode_lock
+    def received_block_announcement(self):
+        return self.block_announced
+
+    def clear_block_announcement(self):
+        with mininode_lock:
+            self.block_announced = False
+            self.last_inv = None
+            self.last_headers = None
+            self.last_cmpctblock = None
+
+    def get_headers(self, locator, hashstop):
+        msg = msg_getheaders()
+        msg.locator.vHave = locator
+        msg.hashstop = hashstop
+        self.connection.send_message(msg)
+
+    def send_header_for_blocks(self, new_blocks):
+        headers_message = msg_headers()
+        headers_message.headers = [CBlockHeader(b) for b in new_blocks]
+        self.send_message(headers_message)
+
+
+class CompactBlocksTest(BitcoinTestFramework):
+    def __init__(self):
+        super().__init__()
+        self.setup_clean_chain = True
+        self.num_nodes = 1
+        self.utxos = []
+
+    def setup_network(self):
+        self.nodes = []
+
+        # Turn off segwit in this test, as compact blocks don't currently work
+        # with segwit.  (After BIP 152 is updated to support segwit, we can
+        # test behavior with and without segwit enabled by adding a second node
+        # to the test.)
+        self.nodes = start_nodes(self.num_nodes, self.options.tmpdir, [["-debug", "-logtimemicros=1", "-bip9params=segwit:0:0"]])
+
+    def build_block_on_tip(self):
+        height = self.nodes[0].getblockcount()
+        tip = self.nodes[0].getbestblockhash()
+        mtp = self.nodes[0].getblockheader(tip)['mediantime']
+        block = create_block(int(tip, 16), create_coinbase(height + 1), mtp + 1)
+        block.solve()
+        return block
+
+    # Create 10 more anyone-can-spend utxo's for testing.
+    def make_utxos(self):
+        block = self.build_block_on_tip()
+        self.test_node.send_and_ping(msg_block(block))
+        assert(int(self.nodes[0].getbestblockhash(), 16) == block.sha256)
+        self.nodes[0].generate(100)
+
+        total_value = block.vtx[0].vout[0].nValue
+        out_value = total_value // 10
+        tx = CTransaction()
+        tx.vin.append(CTxIn(COutPoint(block.vtx[0].sha256, 0), b''))
+        for i in range(10):
+            tx.vout.append(CTxOut(out_value, CScript([OP_TRUE])))
+        tx.rehash()
+
+        block2 = self.build_block_on_tip()
+        block2.vtx.append(tx)
+        block2.hashMerkleRoot = block2.calc_merkle_root()
+        block2.solve()
+        self.test_node.send_and_ping(msg_block(block2))
+        assert_equal(int(self.nodes[0].getbestblockhash(), 16), block2.sha256)
+        self.utxos.extend([[tx.sha256, i, out_value] for i in range(10)])
+        return
+
+    # Test "sendcmpct":
+    # - No compact block announcements or getdata(MSG_CMPCT_BLOCK) unless
+    #   sendcmpct is sent.
+    # - If sendcmpct is sent with version > 0, the message is ignored.
+    # - If sendcmpct is sent with boolean 0, then block announcements are not
+    #   made with compact blocks.
+    # - If sendcmpct is then sent with boolean 1, then new block announcements
+    #   are made with compact blocks.
+    def test_sendcmpct(self):
+        print("Testing SENDCMPCT p2p message... ")
+
+        # Make sure we get a version 0 SENDCMPCT message from our peer
+        def received_sendcmpct():
+            return (self.test_node.last_sendcmpct is not None)
+        got_message = wait_until(received_sendcmpct, timeout=30)
+        assert(got_message)
+        assert_equal(self.test_node.last_sendcmpct.version, 1)
+
+        tip = int(self.nodes[0].getbestblockhash(), 16)
+
+        def check_announcement_of_new_block(node, peer, predicate):
+            self.test_node.clear_block_announcement()
+            node.generate(1)
+            got_message = wait_until(peer.received_block_announcement, timeout=30)
+            assert(got_message)
+            with mininode_lock:
+                assert(predicate)
+
+        # We shouldn't get any block announcements via cmpctblock yet.
+        check_announcement_of_new_block(self.nodes[0], self.test_node, lambda: self.test_node.last_cmpctblock is None)
+
+        # Try one more time, this time after requesting headers.
+        self.test_node.clear_block_announcement()
+        self.test_node.get_headers(locator=[tip], hashstop=0)
+        wait_until(self.test_node.received_block_announcement, timeout=30)
+        self.test_node.clear_block_announcement()
+
+        check_announcement_of_new_block(self.nodes[0], self.test_node, lambda: self.test_node.last_cmpctblock is None and self.test_node.last_inv is not None)
+
+        # Now try a SENDCMPCT message with too-high version
+        sendcmpct = msg_sendcmpct()
+        sendcmpct.version = 2
+        self.test_node.send_message(sendcmpct)
+
+        check_announcement_of_new_block(self.nodes[0], self.test_node, lambda: self.test_node.last_cmpctblock is None)
+
+        # Now try a SENDCMPCT message with valid version, but announce=False
+        self.test_node.send_message(msg_sendcmpct())
+        check_announcement_of_new_block(self.nodes[0], self.test_node, lambda: self.test_node.last_cmpctblock is None)
+
+        # Finally, try a SENDCMPCT message with announce=True
+        sendcmpct.version = 1
+        sendcmpct.announce = True
+        self.test_node.send_message(sendcmpct)
+        check_announcement_of_new_block(self.nodes[0], self.test_node, lambda: self.test_node.last_cmpctblock is not None)
+
+        # Try one more time
+        check_announcement_of_new_block(self.nodes[0], self.test_node, lambda: self.test_node.last_cmpctblock is not None)
+
+        # Try one more time, after turning on sendheaders
+        self.test_node.send_message(msg_sendheaders())
+        check_announcement_of_new_block(self.nodes[0], self.test_node, lambda: self.test_node.last_cmpctblock is not None)
+
+        # Now turn off announcements
+        sendcmpct.announce = False
+        check_announcement_of_new_block(self.nodes[0], self.test_node, lambda: self.test_node.last_cmpctblock is None and self.test_node.last_headers is not None)
+
+    # This test actually causes bitcoind to (reasonably!) disconnect us, so do this last.
+    def test_invalid_cmpctblock_message(self):
+        print("Testing invalid index in cmpctblock message...")
+        self.nodes[0].generate(101)
+        block = self.build_block_on_tip()
+
+        cmpct_block = P2PHeaderAndShortIDs()
+        cmpct_block.header = CBlockHeader(block)
+        cmpct_block.prefilled_txn_length = 1
+        # This index will be too high
+        prefilled_txn = PrefilledTransaction(1, block.vtx[0])
+        cmpct_block.prefilled_txn = [prefilled_txn]
+        self.test_node.send_and_ping(msg_cmpctblock(cmpct_block))
+        assert(int(self.nodes[0].getbestblockhash(), 16) == block.hashPrevBlock)
+
+    # Compare the generated shortids to what we expect based on BIP 152, given
+    # bitcoind's choice of nonce.
+    def test_compactblock_construction(self):
+        print("Testing compactblock headers and shortIDs are correct...")
+
+        # Generate a bunch of transactions.
+        self.nodes[0].generate(101)
+        num_transactions = 25
+        address = self.nodes[0].getnewaddress()
+        for i in range(num_transactions):
+            self.nodes[0].sendtoaddress(address, 0.1)
+
+        # Now mine a block, and look at the resulting compact block.
+        self.test_node.clear_block_announcement()
+        block_hash = int(self.nodes[0].generate(1)[0], 16)
+
+        # Store the raw block in our internal format.
+        block = FromHex(CBlock(), self.nodes[0].getblock("%02x" % block_hash, False))
+        [tx.calc_sha256() for tx in block.vtx]
+        block.rehash()
+
+        # Don't care which type of announcement came back for this test; just
+        # request the compact block if we didn't get one yet.
+        wait_until(self.test_node.received_block_announcement, timeout=30)
+
+        with mininode_lock:
+            if self.test_node.last_cmpctblock is None:
+                self.test_node.clear_block_announcement()
+                inv = CInv(4, block_hash)  # 4 == "CompactBlock"
+                self.test_node.send_message(msg_getdata([inv]))
+
+        wait_until(self.test_node.received_block_announcement, timeout=30)
+
+        # Now we should have the compactblock
+        header_and_shortids = None
+        with mininode_lock:
+            assert(self.test_node.last_cmpctblock is not None)
+            # Convert the on-the-wire representation to absolute indexes
+            header_and_shortids = HeaderAndShortIDs(self.test_node.last_cmpctblock.header_and_shortids)
+
+        # Check that we got the right block!
+        header_and_shortids.header.calc_sha256()
+        assert_equal(header_and_shortids.header.sha256, block_hash)
+
+        # Make sure the prefilled_txn appears to have included the coinbase
+        assert(len(header_and_shortids.prefilled_txn) >= 1)
+        assert_equal(header_and_shortids.prefilled_txn[0].index, 0)
+
+        # Check that all prefilled_txn entries match what's in the block.
+        for entry in header_and_shortids.prefilled_txn:
+            entry.tx.calc_sha256()
+            assert_equal(entry.tx.sha256, block.vtx[entry.index].sha256)
+
+        # Check that the cmpctblock message announced all the transactions.
+        assert_equal(len(header_and_shortids.prefilled_txn) + len(header_and_shortids.shortids), len(block.vtx))
+
+        # And now check that all the shortids are as expected as well.
+        # Determine the siphash keys to use.
+        [k0, k1] = header_and_shortids.get_siphash_keys()
+
+        index = 0
+        while index < len(block.vtx):
+            if (len(header_and_shortids.prefilled_txn) > 0 and
+                    header_and_shortids.prefilled_txn[0].index == index):
+                # Already checked prefilled transactions above
+                header_and_shortids.prefilled_txn.pop(0)
+            else:
+                shortid = calculate_shortid(k0, k1, block.vtx[index].sha256)
+                assert_equal(shortid, header_and_shortids.shortids[0])
+                header_and_shortids.shortids.pop(0)
+            index += 1
+
+    # Test that bitcoind requests compact blocks when we announce new blocks
+    # via header or inv, and that responding to getblocktxn causes the block
+    # to be successfully reconstructed.
+    def test_compactblock_requests(self):
+        print("Testing compactblock requests... ")
+
+        # Try announcing a block with an inv or header, expect a compactblock
+        # request
+        for announce in ["inv", "header"]:
+            block = self.build_block_on_tip()
+            with mininode_lock:
+                self.test_node.last_getdata = None
+
+            if announce == "inv":
+                self.test_node.send_message(msg_inv([CInv(2, block.sha256)]))
+            else:
+                self.test_node.send_header_for_blocks([block])
+            success = wait_until(lambda: self.test_node.last_getdata is not None, timeout=30)
+            assert(success)
+            assert_equal(len(self.test_node.last_getdata.inv), 1)
+            assert_equal(self.test_node.last_getdata.inv[0].type, 4)
+            assert_equal(self.test_node.last_getdata.inv[0].hash, block.sha256)
+
+            # Send back a compactblock message that omits the coinbase
+            comp_block = HeaderAndShortIDs()
+            comp_block.header = CBlockHeader(block)
+            comp_block.nonce = 0
+            comp_block.shortids = [1]  # this is useless, and wrong
+            self.test_node.send_and_ping(msg_cmpctblock(comp_block.to_p2p()))
+            assert_equal(int(self.nodes[0].getbestblockhash(), 16), block.hashPrevBlock)
+            # Expect a getblocktxn message.
+            with mininode_lock:
+                assert(self.test_node.last_getblocktxn is not None)
+                absolute_indexes = self.test_node.last_getblocktxn.block_txn_request.to_absolute()
+            assert_equal(absolute_indexes, [0])  # should be a coinbase request
+
+            # Send the coinbase, and verify that the tip advances.
+            msg = msg_blocktxn()
+            msg.block_transactions.blockhash = block.sha256
+            msg.block_transactions.transactions = [block.vtx[0]]
+            self.test_node.send_and_ping(msg)
+            assert_equal(int(self.nodes[0].getbestblockhash(), 16), block.sha256)
+
+    # Create a chain of transactions from given utxo, and add to a new block.
+    def build_block_with_transactions(self, utxo, num_transactions):
+        block = self.build_block_on_tip()
+
+        for i in range(num_transactions):
+            tx = CTransaction()
+            tx.vin.append(CTxIn(COutPoint(utxo[0], utxo[1]), b''))
+            tx.vout.append(CTxOut(utxo[2] - 1000, CScript([OP_TRUE])))
+            tx.rehash()
+            utxo = [tx.sha256, 0, tx.vout[0].nValue]
+            block.vtx.append(tx)
+
+        block.hashMerkleRoot = block.calc_merkle_root()
+        block.solve()
+        return block
+
+    # Test that we only receive getblocktxn requests for transactions that the
+    # node needs, and that responding to them causes the block to be
+    # reconstructed.
+    def test_getblocktxn_requests(self):
+        print("Testing getblocktxn requests...")
+
+        # First try announcing compactblocks that won't reconstruct, and verify
+        # that we receive getblocktxn messages back.
+        utxo = self.utxos.pop(0)
+
+        block = self.build_block_with_transactions(utxo, 5)
+        self.utxos.append([block.vtx[-1].sha256, 0, block.vtx[-1].vout[0].nValue])
+
+        comp_block = HeaderAndShortIDs()
+        comp_block.initialize_from_block(block)
+
+        self.test_node.send_and_ping(msg_cmpctblock(comp_block.to_p2p()))
+        with mininode_lock:
+            assert(self.test_node.last_getblocktxn is not None)
+            absolute_indexes = self.test_node.last_getblocktxn.block_txn_request.to_absolute()
+        assert_equal(absolute_indexes, [1, 2, 3, 4, 5])
+        msg = msg_blocktxn()
+        msg.block_transactions = BlockTransactions(block.sha256, block.vtx[1:])
+        self.test_node.send_and_ping(msg)
+        assert_equal(int(self.nodes[0].getbestblockhash(), 16), block.sha256)
+
+        utxo = self.utxos.pop(0)
+        block = self.build_block_with_transactions(utxo, 5)
+        self.utxos.append([block.vtx[-1].sha256, 0, block.vtx[-1].vout[0].nValue])
+
+        # Now try interspersing the prefilled transactions
+        comp_block.initialize_from_block(block, prefill_list=[0, 1, 5])
+        self.test_node.send_and_ping(msg_cmpctblock(comp_block.to_p2p()))
+        with mininode_lock:
+            assert(self.test_node.last_getblocktxn is not None)
+            absolute_indexes = self.test_node.last_getblocktxn.block_txn_request.to_absolute()
+        assert_equal(absolute_indexes, [2, 3, 4])
+        msg.block_transactions = BlockTransactions(block.sha256, block.vtx[2:5])
+        self.test_node.send_and_ping(msg)
+        assert_equal(int(self.nodes[0].getbestblockhash(), 16), block.sha256)
+
+        # Now try giving one transaction ahead of time.
+        utxo = self.utxos.pop(0)
+        block = self.build_block_with_transactions(utxo, 5)
+        self.utxos.append([block.vtx[-1].sha256, 0, block.vtx[-1].vout[0].nValue])
+        self.test_node.send_and_ping(msg_tx(block.vtx[1]))
+        assert(block.vtx[1].hash in self.nodes[0].getrawmempool())
+
+        # Prefill 4 out of the 6 transactions, and verify that only the one
+        # that was not in the mempool is requested.
+        comp_block.initialize_from_block(block, prefill_list=[0, 2, 3, 4])
+        self.test_node.send_and_ping(msg_cmpctblock(comp_block.to_p2p()))
+        with mininode_lock:
+            assert(self.test_node.last_getblocktxn is not None)
+            absolute_indexes = self.test_node.last_getblocktxn.block_txn_request.to_absolute()
+        assert_equal(absolute_indexes, [5])
+
+        msg.block_transactions = BlockTransactions(block.sha256, [block.vtx[5]])
+        self.test_node.send_and_ping(msg)
+        assert_equal(int(self.nodes[0].getbestblockhash(), 16), block.sha256)
+
+        # Now provide all transactions to the node before the block is
+        # announced and verify reconstruction happens immediately.
+        utxo = self.utxos.pop(0)
+        block = self.build_block_with_transactions(utxo, 10)
+        self.utxos.append([block.vtx[-1].sha256, 0, block.vtx[-1].vout[0].nValue])
+        for tx in block.vtx[1:]:
+            self.test_node.send_message(msg_tx(tx))
+        self.test_node.sync_with_ping()
+        # Make sure all transactions were accepted.
+        mempool = self.nodes[0].getrawmempool()
+        for tx in block.vtx[1:]:
+            assert(tx.hash in mempool)
+
+        # Clear out last request.
+        with mininode_lock:
+            self.test_node.last_getblocktxn = None
+
+        # Send compact block
+        comp_block.initialize_from_block(block, prefill_list=[0])
+        self.test_node.send_and_ping(msg_cmpctblock(comp_block.to_p2p()))
+        with mininode_lock:
+            # Shouldn't have gotten a request for any transaction
+            assert(self.test_node.last_getblocktxn is None)
+        # Tip should have updated
+        assert_equal(int(self.nodes[0].getbestblockhash(), 16), block.sha256)
+
+    # Incorrectly responding to a getblocktxn shouldn't cause the block to be
+    # permanently failed.
+    def test_incorrect_blocktxn_response(self):
+        print("Testing handling of incorrect blocktxn responses...")
+
+        if (len(self.utxos) == 0):
+            self.make_utxos()
+        utxo = self.utxos.pop(0)
+
+        block = self.build_block_with_transactions(utxo, 10)
+        self.utxos.append([block.vtx[-1].sha256, 0, block.vtx[-1].vout[0].nValue])
+        # Relay the first 5 transactions from the block in advance
+        for tx in block.vtx[1:6]:
+            self.test_node.send_message(msg_tx(tx))
+        self.test_node.sync_with_ping()
+        # Make sure all transactions were accepted.
+        mempool = self.nodes[0].getrawmempool()
+        for tx in block.vtx[1:6]:
+            assert(tx.hash in mempool)
+
+        # Send compact block
+        comp_block = HeaderAndShortIDs()
+        comp_block.initialize_from_block(block, prefill_list=[0])
+        self.test_node.send_and_ping(msg_cmpctblock(comp_block.to_p2p()))
+        absolute_indexes = []
+        with mininode_lock:
+            assert(self.test_node.last_getblocktxn is not None)
+            absolute_indexes = self.test_node.last_getblocktxn.block_txn_request.to_absolute()
+        assert_equal(absolute_indexes, [6, 7, 8, 9, 10])
+
+        # Now give an incorrect response.
+        # Note that it's possible for bitcoind to be smart enough to know we're
+        # lying, since it could check to see if the shortid matches what we're
+        # sending, and eg disconnect us for misbehavior.  If that behavior
+        # change were made, we could just modify this test by having a
+        # different peer provide the block further down, so that we're still
+        # verifying that the block isn't marked bad permanently. This is good
+        # enough for now.
+        msg = msg_blocktxn()
+        msg.block_transactions = BlockTransactions(block.sha256, [block.vtx[5]] + block.vtx[7:])
+        self.test_node.send_and_ping(msg)
+
+        # Tip should not have updated
+        assert_equal(int(self.nodes[0].getbestblockhash(), 16), block.hashPrevBlock)
+
+        # We should receive a getdata request
+        success = wait_until(lambda: self.test_node.last_getdata is not None, timeout=10)
+        assert(success)
+        assert_equal(len(self.test_node.last_getdata.inv), 1)
+        assert_equal(self.test_node.last_getdata.inv[0].type, 2)
+        assert_equal(self.test_node.last_getdata.inv[0].hash, block.sha256)
+
+        # Deliver the block
+        self.test_node.send_and_ping(msg_block(block))
+        assert_equal(int(self.nodes[0].getbestblockhash(), 16), block.sha256)
+
+    def test_getblocktxn_handler(self):
+        print("Testing getblocktxn handler...")
+
+        # bitcoind won't respond for blocks whose height is more than 15 blocks
+        # deep.
+        MAX_GETBLOCKTXN_DEPTH = 15
+        chain_height = self.nodes[0].getblockcount()
+        current_height = chain_height
+        while (current_height >= chain_height - MAX_GETBLOCKTXN_DEPTH):
+            block_hash = self.nodes[0].getblockhash(current_height)
+            block = FromHex(CBlock(), self.nodes[0].getblock(block_hash, False))
+
+            msg = msg_getblocktxn()
+            msg.block_txn_request = BlockTransactionsRequest(int(block_hash, 16), [])
+            num_to_request = random.randint(1, len(block.vtx))
+            msg.block_txn_request.from_absolute(sorted(random.sample(range(len(block.vtx)), num_to_request)))
+            self.test_node.send_message(msg)
+            success = wait_until(lambda: self.test_node.last_blocktxn is not None, timeout=10)
+            assert(success)
+
+            [tx.calc_sha256() for tx in block.vtx]
+            with mininode_lock:
+                assert_equal(self.test_node.last_blocktxn.block_transactions.blockhash, int(block_hash, 16))
+                all_indices = msg.block_txn_request.to_absolute()
+                for index in all_indices:
+                    tx = self.test_node.last_blocktxn.block_transactions.transactions.pop(0)
+                    tx.calc_sha256()
+                    assert_equal(tx.sha256, block.vtx[index].sha256)
+                self.test_node.last_blocktxn = None
+            current_height -= 1
+
+        # Next request should be ignored, as we're past the allowed depth.
+        block_hash = self.nodes[0].getblockhash(current_height)
+        msg.block_txn_request = BlockTransactionsRequest(int(block_hash, 16), [0])
+        self.test_node.send_and_ping(msg)
+        with mininode_lock:
+            assert_equal(self.test_node.last_blocktxn, None)
+
+    def test_compactblocks_not_at_tip(self):
+        print("Testing compactblock requests/announcements not at chain tip...")
+
+        # Test that requesting old compactblocks doesn't work.
+        MAX_CMPCTBLOCK_DEPTH = 11
+        new_blocks = []
+        for i in range(MAX_CMPCTBLOCK_DEPTH):
+            self.test_node.clear_block_announcement()
+            new_blocks.append(self.nodes[0].generate(1)[0])
+            wait_until(self.test_node.received_block_announcement, timeout=30)
+
+        self.test_node.clear_block_announcement()
+        self.test_node.send_message(msg_getdata([CInv(4, int(new_blocks[0], 16))]))
+        success = wait_until(lambda: self.test_node.last_cmpctblock is not None, timeout=30)
+        assert(success)
+
+        self.test_node.clear_block_announcement()
+        self.nodes[0].generate(1)
+        wait_until(self.test_node.received_block_announcement, timeout=30)
+        self.test_node.clear_block_announcement()
+        self.test_node.send_message(msg_getdata([CInv(4, int(new_blocks[0], 16))]))
+        success = wait_until(lambda: self.test_node.last_block is not None, timeout=30)
+        assert(success)
+        with mininode_lock:
+            self.test_node.last_block.block.calc_sha256()
+            assert_equal(self.test_node.last_block.block.sha256, int(new_blocks[0], 16))
+
+        # Generate an old compactblock, and verify that it's not accepted.
+        cur_height = self.nodes[0].getblockcount()
+        hashPrevBlock = int(self.nodes[0].getblockhash(cur_height-5), 16)
+        block = self.build_block_on_tip()
+        block.hashPrevBlock = hashPrevBlock
+        block.solve()
+
+        comp_block = HeaderAndShortIDs()
+        comp_block.initialize_from_block(block)
+        self.test_node.send_and_ping(msg_cmpctblock(comp_block.to_p2p()))
+
+        tips = self.nodes[0].getchaintips()
+        found = False
+        for x in tips:
+            if x["hash"] == block.hash:
+                assert_equal(x["status"], "headers-only")
+                found = True
+                break
+        assert(found)
+
+        # Requesting this block via getblocktxn should silently fail
+        # (to avoid fingerprinting attacks).
+        msg = msg_getblocktxn()
+        msg.block_txn_request = BlockTransactionsRequest(block.sha256, [0])
+        with mininode_lock:
+            self.test_node.last_blocktxn = None
+        self.test_node.send_and_ping(msg)
+        with mininode_lock:
+            assert(self.test_node.last_blocktxn is None)
+
+    def run_test(self):
+        # Setup the p2p connections and start up the network thread.
+        self.test_node = TestNode()
+
+        connections = []
+        connections.append(NodeConn('127.0.0.1', p2p_port(0), self.nodes[0], self.test_node))
+        self.test_node.add_connection(connections[0])
+
+        NetworkThread().start()  # Start up network handling in another thread
+
+        # Test logic begins here
+        self.test_node.wait_for_verack()
+
+        # We will need UTXOs to construct transactions in later tests.
+        self.make_utxos()
+
+        self.test_sendcmpct()
+        self.test_compactblock_construction()
+        self.test_compactblock_requests()
+        self.test_getblocktxn_requests()
+        self.test_getblocktxn_handler()
+        self.test_compactblocks_not_at_tip()
+        self.test_incorrect_blocktxn_response()
+        self.test_invalid_cmpctblock_message()
+
+
+if __name__ == '__main__':
+    CompactBlocksTest().main()
diff --git a/qa/rpc-tests/test_framework/mininode.py b/qa/rpc-tests/test_framework/mininode.py
index cdd5292cd..caffab353 100755
--- a/qa/rpc-tests/test_framework/mininode.py
+++ b/qa/rpc-tests/test_framework/mininode.py
@@ -36,9 +36,10 @@ from threading import RLock
 from threading import Thread
 import logging
 import copy
+from test_framework.siphash import siphash256
 
 BIP0031_VERSION = 60000
-MY_VERSION = 60001  # past bip-31 for ping/pong
+MY_VERSION = 70014  # past bip-31 for ping/pong
 MY_SUBVERSION = b"/python-mininode-tester:0.0.3/"
 
 MAX_INV_SZ = 50000
@@ -52,7 +53,7 @@ NODE_BLOOM = (1 << 2)
 NODE_WITNESS = (1 << 3)
 
 # Keep our own socket map for asyncore, so that we can track disconnects
-# ourselves (to workaround an issue with closing an asyncore socket when 
+# ourselves (to workaround an issue with closing an asyncore socket when
 # using select)
 mininode_socket_map = dict()
 
@@ -74,8 +75,19 @@ def ripemd160(s):
 def hash256(s):
     return sha256(sha256(s))
 
+def ser_compact_size(l):
+    r = b""
+    if l < 253:
+        r = struct.pack("B", l)
+    elif l < 0x10000:
+        r = struct.pack("<BH", 253, l)
+    elif l < 0x100000000:
+        r = struct.pack("<BI", 254, l)
+    else:
+        r = struct.pack("<BQ", 255, l)
+    return r
 
-def deser_string(f):
+def deser_compact_size(f):
     nit = struct.unpack("<B", f.read(1))[0]
     if nit == 253:
         nit = struct.unpack("<H", f.read(2))[0]
@@ -83,16 +95,14 @@ def deser_string(f):
         nit = struct.unpack("<I", f.read(4))[0]
     elif nit == 255:
         nit = struct.unpack("<Q", f.read(8))[0]
+    return nit
+
+def deser_string(f):
+    nit = deser_compact_size(f)
     return f.read(nit)
 
 def ser_string(s):
-    if len(s) < 253:
-        return struct.pack("B", len(s)) + s
-    elif len(s) < 0x10000:
-        return struct.pack("<BH", 253, len(s)) + s
-    elif len(s) < 0x100000000:
-        return struct.pack("<BI", 254, len(s)) + s
-    return struct.pack("<BQ", 255, len(s)) + s
+    return ser_compact_size(len(s)) + s
 
 def deser_uint256(f):
     r = 0
@@ -125,13 +135,7 @@ def uint256_from_compact(c):
 
 
 def deser_vector(f, c):
-    nit = struct.unpack("<B", f.read(1))[0]
-    if nit == 253:
-        nit = struct.unpack("<H", f.read(2))[0]
-    elif nit == 254:
-        nit = struct.unpack("<I", f.read(4))[0]
-    elif nit == 255:
-        nit = struct.unpack("<Q", f.read(8))[0]
+    nit = deser_compact_size(f)
     r = []
     for i in range(nit):
         t = c()
@@ -144,15 +148,7 @@ def deser_vector(f, c):
 # entries in the vector (we use this for serializing the vector of transactions
 # for a witness block).
 def ser_vector(l, ser_function_name=None):
-    r = b""
-    if len(l) < 253:
-        r = struct.pack("B", len(l))
-    elif len(l) < 0x10000:
-        r = struct.pack("<BH", 253, len(l))
-    elif len(l) < 0x100000000:
-        r = struct.pack("<BI", 254, len(l))
-    else:
-        r = struct.pack("<BQ", 255, len(l))
+    r = ser_compact_size(len(l))
     for i in l:
         if ser_function_name:
             r += getattr(i, ser_function_name)()
@@ -162,13 +158,7 @@ def ser_vector(l, ser_function_name=None):
 
 
 def deser_uint256_vector(f):
-    nit = struct.unpack("<B", f.read(1))[0]
-    if nit == 253:
-        nit = struct.unpack("<H", f.read(2))[0]
-    elif nit == 254:
-        nit = struct.unpack("<I", f.read(4))[0]
-    elif nit == 255:
-        nit = struct.unpack("<Q", f.read(8))[0]
+    nit = deser_compact_size(f)
     r = []
     for i in range(nit):
         t = deser_uint256(f)
@@ -177,28 +167,14 @@ def deser_uint256_vector(f):
 
 
 def ser_uint256_vector(l):
-    r = b""
-    if len(l) < 253:
-        r = struct.pack("B", len(l))
-    elif len(l) < 0x10000:
-        r = struct.pack("<BH", 253, len(l))
-    elif len(l) < 0x100000000:
-        r = struct.pack("<BI", 254, len(l))
-    else:
-        r = struct.pack("<BQ", 255, len(l))
+    r = ser_compact_size(len(l))
     for i in l:
         r += ser_uint256(i)
     return r
 
 
 def deser_string_vector(f):
-    nit = struct.unpack("<B", f.read(1))[0]
-    if nit == 253:
-        nit = struct.unpack("<H", f.read(2))[0]
-    elif nit == 254:
-        nit = struct.unpack("<I", f.read(4))[0]
-    elif nit == 255:
-        nit = struct.unpack("<Q", f.read(8))[0]
+    nit = deser_compact_size(f)
     r = []
     for i in range(nit):
         t = deser_string(f)
@@ -207,28 +183,14 @@ def deser_string_vector(f):
 
 
 def ser_string_vector(l):
-    r = b""
-    if len(l) < 253:
-        r = struct.pack("B", len(l))
-    elif len(l) < 0x10000:
-        r = struct.pack("<BH", 253, len(l))
-    elif len(l) < 0x100000000:
-        r = struct.pack("<BI", 254, len(l))
-    else:
-        r = struct.pack("<BQ", 255, len(l))
+    r = ser_compact_size(len(l))
     for sv in l:
         r += ser_string(sv)
     return r
 
 
 def deser_int_vector(f):
-    nit = struct.unpack("<B", f.read(1))[0]
-    if nit == 253:
-        nit = struct.unpack("<H", f.read(2))[0]
-    elif nit == 254:
-        nit = struct.unpack("<I", f.read(4))[0]
-    elif nit == 255:
-        nit = struct.unpack("<Q", f.read(8))[0]
+    nit = deser_compact_size(f)
     r = []
     for i in range(nit):
         t = struct.unpack("<i", f.read(4))[0]
@@ -237,15 +199,7 @@ def deser_int_vector(f):
 
 
 def ser_int_vector(l):
-    r = b""
-    if len(l) < 253:
-        r = struct.pack("B", len(l))
-    elif len(l) < 0x10000:
-        r = struct.pack("<BH", 253, len(l))
-    elif len(l) < 0x100000000:
-        r = struct.pack("<BI", 254, len(l))
-    else:
-        r = struct.pack("<BQ", 255, len(l))
+    r = ser_compact_size(len(l))
     for i in l:
         r += struct.pack("<i", i)
     return r
@@ -294,7 +248,8 @@ class CInv(object):
         1: "TX",
         2: "Block",
         1|MSG_WITNESS_FLAG: "WitnessTx",
-        2|MSG_WITNESS_FLAG : "WitnessBlock"
+        2|MSG_WITNESS_FLAG : "WitnessBlock",
+        4: "CompactBlock"
     }
 
     def __init__(self, t=0, h=0):
@@ -781,6 +736,187 @@ class CAlert(object):
             % (len(self.vchMsg), len(self.vchSig))
 
 
+class PrefilledTransaction(object):
+    def __init__(self, index=0, tx = None):
+        self.index = index
+        self.tx = tx
+
+    def deserialize(self, f):
+        self.index = deser_compact_size(f)
+        self.tx = CTransaction()
+        self.tx.deserialize(f)
+
+    def serialize(self, with_witness=False):
+        r = b""
+        r += ser_compact_size(self.index)
+        if with_witness:
+            r += self.tx.serialize_with_witness()
+        else:
+            r += self.tx.serialize_without_witness()
+        return r
+
+    def __repr__(self):
+        return "PrefilledTransaction(index=%d, tx=%s)" % (self.index, repr(self.tx))
+
+# This is what we send on the wire, in a cmpctblock message.
+class P2PHeaderAndShortIDs(object):
+    def __init__(self):
+        self.header = CBlockHeader()
+        self.nonce = 0
+        self.shortids_length = 0
+        self.shortids = []
+        self.prefilled_txn_length = 0
+        self.prefilled_txn = []
+
+    def deserialize(self, f):
+        self.header.deserialize(f)
+        self.nonce = struct.unpack("<Q", f.read(8))[0]
+        self.shortids_length = deser_compact_size(f)
+        for i in range(self.shortids_length):
+            # shortids are defined to be 6 bytes in the spec, so append
+            # two zero bytes and read it in as an 8-byte number
+            self.shortids.append(struct.unpack("<Q", f.read(6) + b'\x00\x00')[0])
+        self.prefilled_txn = deser_vector(f, PrefilledTransaction)
+        self.prefilled_txn_length = len(self.prefilled_txn)
+
+    def serialize(self, with_witness=False):
+        r = b""
+        r += self.header.serialize()
+        r += struct.pack("<Q", self.nonce)
+        r += ser_compact_size(self.shortids_length)
+        for x in self.shortids:
+            # We only want the first 6 bytes
+            r += struct.pack("<Q", x)[0:6]
+        r += ser_vector(self.prefilled_txn)
+        return r
+
+    def __repr__(self):
+        return "P2PHeaderAndShortIDs(header=%s, nonce=%d, shortids_length=%d, shortids=%s, prefilled_txn_length=%d, prefilledtxn=%s" % (repr(self.header), self.nonce, self.shortids_length, repr(self.shortids), self.prefilled_txn_length, repr(self.prefilled_txn))
+
+
+# Calculate the BIP 152-compact blocks shortid for a given transaction hash
+def calculate_shortid(k0, k1, tx_hash):
+    expected_shortid = siphash256(k0, k1, tx_hash)
+    expected_shortid &= 0x0000ffffffffffff
+    return expected_shortid
+
+# This version gets rid of the array lengths, and reinterprets the differential
+# encoding into indices that can be used for lookup.
+class HeaderAndShortIDs(object):
+    def __init__(self, p2pheaders_and_shortids = None):
+        self.header = CBlockHeader()
+        self.nonce = 0
+        self.shortids = []
+        self.prefilled_txn = []
+
+        if p2pheaders_and_shortids != None:
+            self.header = p2pheaders_and_shortids.header
+            self.nonce = p2pheaders_and_shortids.nonce
+            self.shortids = p2pheaders_and_shortids.shortids
+            last_index = -1
+            for x in p2pheaders_and_shortids.prefilled_txn:
+                self.prefilled_txn.append(PrefilledTransaction(x.index + last_index + 1, x.tx))
+                last_index = self.prefilled_txn[-1].index
+
+    def to_p2p(self):
+        ret = P2PHeaderAndShortIDs()
+        ret.header = self.header
+        ret.nonce = self.nonce
+        ret.shortids_length = len(self.shortids)
+        ret.shortids = self.shortids
+        ret.prefilled_txn_length = len(self.prefilled_txn)
+        ret.prefilled_txn = []
+        last_index = -1
+        for x in self.prefilled_txn:
+            ret.prefilled_txn.append(PrefilledTransaction(x.index - last_index - 1, x.tx))
+            last_index = x.index
+        return ret
+
+    def get_siphash_keys(self):
+        header_nonce = self.header.serialize()
+        header_nonce += struct.pack("<Q", self.nonce)
+        hash_header_nonce_as_str = sha256(header_nonce)
+        key0 = struct.unpack("<Q", hash_header_nonce_as_str[0:8])[0]
+        key1 = struct.unpack("<Q", hash_header_nonce_as_str[8:16])[0]
+        return [ key0, key1 ]
+
+    def initialize_from_block(self, block, nonce=0, prefill_list = [0]):
+        self.header = CBlockHeader(block)
+        self.nonce = nonce
+        self.prefilled_txn = [ PrefilledTransaction(i, block.vtx[i]) for i in prefill_list ]
+        self.shortids = []
+        [k0, k1] = self.get_siphash_keys()
+        for i in range(len(block.vtx)):
+            if i not in prefill_list:
+                self.shortids.append(calculate_shortid(k0, k1, block.vtx[i].sha256))
+
+    def __repr__(self):
+        return "HeaderAndShortIDs(header=%s, nonce=%d, shortids=%s, prefilledtxn=%s" % (repr(self.header), self.nonce, repr(self.shortids), repr(self.prefilled_txn))
+
+
+class BlockTransactionsRequest(object):
+
+    def __init__(self, blockhash=0, indexes = None):
+        self.blockhash = blockhash
+        self.indexes = indexes if indexes != None else []
+
+    def deserialize(self, f):
+        self.blockhash = deser_uint256(f)
+        indexes_length = deser_compact_size(f)
+        for i in range(indexes_length):
+            self.indexes.append(deser_compact_size(f))
+
+    def serialize(self):
+        r = b""
+        r += ser_uint256(self.blockhash)
+        r += ser_compact_size(len(self.indexes))
+        for x in self.indexes:
+            r += ser_compact_size(x)
+        return r
+
+    # helper to set the differentially encoded indexes from absolute ones
+    def from_absolute(self, absolute_indexes):
+        self.indexes = []
+        last_index = -1
+        for x in absolute_indexes:
+            self.indexes.append(x-last_index-1)
+            last_index = x
+
+    def to_absolute(self):
+        absolute_indexes = []
+        last_index = -1
+        for x in self.indexes:
+            absolute_indexes.append(x+last_index+1)
+            last_index = absolute_indexes[-1]
+        return absolute_indexes
+
+    def __repr__(self):
+        return "BlockTransactionsRequest(hash=%064x indexes=%s)" % (self.blockhash, repr(self.indexes))
+
+
+class BlockTransactions(object):
+
+    def __init__(self, blockhash=0, transactions = None):
+        self.blockhash = blockhash
+        self.transactions = transactions if transactions != None else []
+
+    def deserialize(self, f):
+        self.blockhash = deser_uint256(f)
+        self.transactions = deser_vector(f, CTransaction)
+
+    def serialize(self, with_witness=False):
+        r = b""
+        r += ser_uint256(self.blockhash)
+        if with_witness:
+            r += ser_vector(self.transactions, "serialize_with_witness")
+        else:
+            r += ser_vector(self.transactions)
+        return r
+
+    def __repr__(self):
+        return "BlockTransactions(hash=%064x transactions=%s)" % (self.blockhash, repr(self.transactions))
+
+
 # Objects that correspond to messages on the wire
 class msg_version(object):
     command = b"version"
@@ -1215,6 +1351,79 @@ class msg_feefilter(object):
     def __repr__(self):
         return "msg_feefilter(feerate=%08x)" % self.feerate
 
+class msg_sendcmpct(object):
+    command = b"sendcmpct"
+
+    def __init__(self):
+        self.announce = False
+        self.version = 1
+
+    def deserialize(self, f):
+        self.announce = struct.unpack("<?", f.read(1))[0]
+        self.version = struct.unpack("<Q", f.read(8))[0]
+
+    def serialize(self):
+        r = b""
+        r += struct.pack("<?", self.announce)
+        r += struct.pack("<Q", self.version)
+        return r
+
+    def __repr__(self):
+        return "msg_sendcmpct(announce=%s, version=%lu)" % (self.announce, self.version)
+
+class msg_cmpctblock(object):
+    command = b"cmpctblock"
+
+    def __init__(self, header_and_shortids = None):
+        self.header_and_shortids = header_and_shortids
+
+    def deserialize(self, f):
+        self.header_and_shortids = P2PHeaderAndShortIDs()
+        self.header_and_shortids.deserialize(f)
+
+    def serialize(self):
+        r = b""
+        r += self.header_and_shortids.serialize()
+        return r
+
+    def __repr__(self):
+        return "msg_cmpctblock(HeaderAndShortIDs=%s)" % repr(self.header_and_shortids)
+
+class msg_getblocktxn(object):
+    command = b"getblocktxn"
+
+    def __init__(self):
+        self.block_txn_request = None
+
+    def deserialize(self, f):
+        self.block_txn_request = BlockTransactionsRequest()
+        self.block_txn_request.deserialize(f)
+
+    def serialize(self):
+        r = b""
+        r += self.block_txn_request.serialize()
+        return r
+
+    def __repr__(self):
+        return "msg_getblocktxn(block_txn_request=%s)" % (repr(self.block_txn_request))
+
+class msg_blocktxn(object):
+    command = b"blocktxn"
+
+    def __init__(self):
+        self.block_transactions = BlockTransactions()
+
+    def deserialize(self, f):
+        self.block_transactions.deserialize(f)
+
+    def serialize(self):
+        r = b""
+        r += self.block_transactions.serialize()
+        return r
+
+    def __repr__(self):
+        return "msg_blocktxn(block_transactions=%s)" % (repr(self.block_transactions))
+
 # This is what a callback should look like for NodeConn
 # Reimplement the on_* functions to provide handling for events
 class NodeConnCB(object):
@@ -1295,6 +1504,10 @@ class NodeConnCB(object):
     def on_pong(self, conn, message): pass
     def on_feefilter(self, conn, message): pass
     def on_sendheaders(self, conn, message): pass
+    def on_sendcmpct(self, conn, message): pass
+    def on_cmpctblock(self, conn, message): pass
+    def on_getblocktxn(self, conn, message): pass
+    def on_blocktxn(self, conn, message): pass
 
 # More useful callbacks and functions for NodeConnCB's which have a single NodeConn
 class SingleNodeConnCB(NodeConnCB):
@@ -1311,6 +1524,10 @@ class SingleNodeConnCB(NodeConnCB):
     def send_message(self, message):
         self.connection.send_message(message)
 
+    def send_and_ping(self, message):
+        self.send_message(message)
+        self.sync_with_ping()
+
     def on_pong(self, conn, message):
         self.last_pong = message
 
@@ -1344,7 +1561,11 @@ class NodeConn(asyncore.dispatcher):
         b"reject": msg_reject,
         b"mempool": msg_mempool,
         b"feefilter": msg_feefilter,
-        b"sendheaders": msg_sendheaders
+        b"sendheaders": msg_sendheaders,
+        b"sendcmpct": msg_sendcmpct,
+        b"cmpctblock": msg_cmpctblock,
+        b"getblocktxn": msg_getblocktxn,
+        b"blocktxn": msg_blocktxn
     }
     MAGIC_BYTES = {
         "mainnet": b"\xf9\xbe\xb4\xd9",   # mainnet
diff --git a/qa/rpc-tests/test_framework/siphash.py b/qa/rpc-tests/test_framework/siphash.py
new file mode 100644
index 000000000..9c0574bd9
--- /dev/null
+++ b/qa/rpc-tests/test_framework/siphash.py
@@ -0,0 +1,64 @@
+#!/usr/bin/env python3
+# Copyright (c) 2016 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#
+# siphash.py - Specialized SipHash-2-4 implementations
+#
+# This implements SipHash-2-4 for 256-bit integers.
+
+def rotl64(n, b):
+    return n >> (64 - b) | (n & ((1 << (64 - b)) - 1)) << b
+
+def siphash_round(v0, v1, v2, v3):
+    v0 = (v0 + v1) & ((1 << 64) - 1)
+    v1 = rotl64(v1, 13)
+    v1 ^= v0
+    v0 = rotl64(v0, 32)
+    v2 = (v2 + v3) & ((1 << 64) - 1)
+    v3 = rotl64(v3, 16)
+    v3 ^= v2
+    v0 = (v0 + v3) & ((1 << 64) - 1)
+    v3 = rotl64(v3, 21)
+    v3 ^= v0
+    v2 = (v2 + v1) & ((1 << 64) - 1)
+    v1 = rotl64(v1, 17)
+    v1 ^= v2
+    v2 = rotl64(v2, 32)
+    return (v0, v1, v2, v3)
+
+def siphash256(k0, k1, h):
+    n0 = h & ((1 << 64) - 1)
+    n1 = (h >> 64) & ((1 << 64) - 1)
+    n2 = (h >> 128) & ((1 << 64) - 1)
+    n3 = (h >> 192) & ((1 << 64) - 1)
+    v0 = 0x736f6d6570736575 ^ k0
+    v1 = 0x646f72616e646f6d ^ k1
+    v2 = 0x6c7967656e657261 ^ k0
+    v3 = 0x7465646279746573 ^ k1 ^ n0
+    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
+    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
+    v0 ^= n0
+    v3 ^= n1
+    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
+    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
+    v0 ^= n1
+    v3 ^= n2
+    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
+    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
+    v0 ^= n2
+    v3 ^= n3
+    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
+    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
+    v0 ^= n3
+    v3 ^= 0x2000000000000000
+    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
+    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
+    v0 ^= 0x2000000000000000
+    v2 ^= 0xFF
+    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
+    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
+    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
+    v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
+    return v0 ^ v1 ^ v2 ^ v3
diff --git a/src/chainparams.cpp b/src/chainparams.cpp
index 86bef1e10..d6032440e 100644
--- a/src/chainparams.cpp
+++ b/src/chainparams.cpp
@@ -303,6 +303,12 @@ public:
         base58Prefixes[EXT_PUBLIC_KEY] = boost::assign::list_of(0x04)(0x35)(0x87)(0xCF).convert_to_container<std::vector<unsigned char> >();
         base58Prefixes[EXT_SECRET_KEY] = boost::assign::list_of(0x04)(0x35)(0x83)(0x94).convert_to_container<std::vector<unsigned char> >();
     }
+
+    void UpdateBIP9Parameters(Consensus::DeploymentPos d, int64_t nStartTime, int64_t nTimeout)
+    {
+        consensus.vDeployments[d].nStartTime = nStartTime;
+        consensus.vDeployments[d].nTimeout = nTimeout;
+    }
 };
 static CRegTestParams regTestParams;
 
@@ -330,4 +336,9 @@ void SelectParams(const std::string& network)
     SelectBaseParams(network);
     pCurrentParams = &Params(network);
 }
+
+void UpdateRegtestBIP9Parameters(Consensus::DeploymentPos d, int64_t nStartTime, int64_t nTimeout)
+{
+    regTestParams.UpdateBIP9Parameters(d, nStartTime, nTimeout);
+}
  
diff --git a/src/chainparams.h b/src/chainparams.h
index 638893e9a..0c3820b7c 100644
--- a/src/chainparams.h
+++ b/src/chainparams.h
@@ -112,4 +112,9 @@ CChainParams& Params(const std::string& chain);
  */
 void SelectParams(const std::string& chain);
 
+/**
+ * Allows modifying the BIP9 regtest parameters.
+ */
+void UpdateRegtestBIP9Parameters(Consensus::DeploymentPos d, int64_t nStartTime, int64_t nTimeout);
+
 #endif // BITCOIN_CHAINPARAMS_H
diff --git a/src/init.cpp b/src/init.cpp
index 8d4a2cafb..5dc3ac023 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -410,6 +410,7 @@ std::string HelpMessage(HelpMessageMode mode)
         strUsage += HelpMessageOpt("-limitancestorsize=<n>", strprintf("Do not accept transactions whose size with all in-mempool ancestors exceeds <n> kilobytes (default: %u)", DEFAULT_ANCESTOR_SIZE_LIMIT));
         strUsage += HelpMessageOpt("-limitdescendantcount=<n>", strprintf("Do not accept transactions if any ancestor would have <n> or more in-mempool descendants (default: %u)", DEFAULT_DESCENDANT_LIMIT));
         strUsage += HelpMessageOpt("-limitdescendantsize=<n>", strprintf("Do not accept transactions if any ancestor would have more than <n> kilobytes of in-mempool descendants (default: %u).", DEFAULT_DESCENDANT_SIZE_LIMIT));
+        strUsage += HelpMessageOpt("-bip9params=deployment:start:end", "Use given start/end times for specified bip9 deployment (regtest-only)");
     }
     string debugCategories = "addrman, alert, bench, coindb, db, http, libevent, lock, mempool, mempoolrej, net, proxy, prune, rand, reindex, rpc, selectcoins, tor, zmq"; // Don't translate these and qt below
     if (mode == HMM_BITCOIN_QT)
@@ -975,6 +976,41 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
         fEnableReplacement = (std::find(vstrReplacementModes.begin(), vstrReplacementModes.end(), "fee") != vstrReplacementModes.end());
     }
 
+    if (!mapMultiArgs["-bip9params"].empty()) {
+        // Allow overriding bip9 parameters for testing
+        if (!Params().MineBlocksOnDemand()) {
+            return InitError("BIP9 parameters may only be overridden on regtest.");
+        }
+        const vector<string>& deployments = mapMultiArgs["-bip9params"];
+        for (auto i : deployments) {
+            std::vector<std::string> vDeploymentParams;
+            boost::split(vDeploymentParams, i, boost::is_any_of(":"));
+            if (vDeploymentParams.size() != 3) {
+                return InitError("BIP9 parameters malformed, expecting deployment:start:end");
+            }
+            int64_t nStartTime, nTimeout;
+            if (!ParseInt64(vDeploymentParams[1], &nStartTime)) {
+                return InitError(strprintf("Invalid nStartTime (%s)", vDeploymentParams[1]));
+            }
+            if (!ParseInt64(vDeploymentParams[2], &nTimeout)) {
+                return InitError(strprintf("Invalid nTimeout (%s)", vDeploymentParams[2]));
+            }
+            bool found = false;
+            for (int i=0; i<(int)Consensus::MAX_VERSION_BITS_DEPLOYMENTS; ++i)
+            {
+                if (vDeploymentParams[0].compare(VersionBitsDeploymentInfo[i].name) == 0) {
+                    UpdateRegtestBIP9Parameters(Consensus::DeploymentPos(i), nStartTime, nTimeout);
+                    found = true;
+                    LogPrintf("Setting BIP9 activation parameters for %s to start=%ld, timeout=%ld\n", vDeploymentParams[0], nStartTime, nTimeout);
+                    break;
+                }
+            }
+            if (!found) {
+                return InitError(strprintf("Invalid deployment (%s)", vDeploymentParams[0]));
+            }
+        }
+    }
+
     // ********************************************************* Step 4: application initialization: dir lock, daemonize, pidfile, debug log
 
     // Initialize elliptic curve code
diff --git a/src/test/hash_tests.cpp b/src/test/hash_tests.cpp
index 82d61209b..fa9624f13 100644
--- a/src/test/hash_tests.cpp
+++ b/src/test/hash_tests.cpp
@@ -122,6 +122,10 @@ BOOST_AUTO_TEST_CASE(siphash)
         hasher3.Write(uint64_t(x)|(uint64_t(x+1)<<8)|(uint64_t(x+2)<<16)|(uint64_t(x+3)<<24)|
                      (uint64_t(x+4)<<32)|(uint64_t(x+5)<<40)|(uint64_t(x+6)<<48)|(uint64_t(x+7)<<56));
     }
+
+    CHashWriter ss(SER_DISK, CLIENT_VERSION);
+    ss << CTransaction();
+    BOOST_CHECK_EQUAL(SipHashUint256(1, 2, ss.GetHash()), 0x79751e980c2a0a35ULL);
 }
 
 BOOST_AUTO_TEST_SUITE_END()