diff --git a/src/miner.cpp b/src/miner.cpp
index a3e29431d..f2ad1018b 100644
--- a/src/miner.cpp
+++ b/src/miner.cpp
@@ -236,14 +236,19 @@ bool BlockAssembler::TestPackage(uint64_t packageSize, int64_t packageSigOpsCost
     return true;
 }
 
-// Block size and sigops have already been tested.  Check that all transactions
-// are final.
-bool BlockAssembler::TestPackageFinalityAndSerializedSize(const CTxMemPool::setEntries& package)
+// Perform transaction-level checks before adding to block:
+// - transaction finality (locktime)
+// - premature witness (in case segwit transactions are added to mempool before
+//   segwit activation)
+// - serialized size (in case -blockmaxsize is in use)
+bool BlockAssembler::TestPackageTransactions(const CTxMemPool::setEntries& package)
 {
     uint64_t nPotentialBlockSize = nBlockSize; // only used with fNeedSizeAccounting
     BOOST_FOREACH (const CTxMemPool::txiter it, package) {
         if (!IsFinalTx(it->GetTx(), nHeight, nLockTimeCutoff))
             return false;
+        if (!fIncludeWitness && !it->GetTx().wit.IsNull())
+            return false;
         if (fNeedSizeAccounting) {
             uint64_t nTxSize = ::GetSerializeSize(it->GetTx(), SER_NETWORK, PROTOCOL_VERSION);
             if (nPotentialBlockSize + nTxSize >= nBlockMaxSize) {
@@ -542,7 +547,7 @@ void BlockAssembler::addPackageTxs()
         ancestors.insert(iter);
 
         // Test if all tx's are Final
-        if (!TestPackageFinalityAndSerializedSize(ancestors)) {
+        if (!TestPackageTransactions(ancestors)) {
             if (fUsingModified) {
                 mapModifiedTx.get<ancestor_score>().erase(modit);
                 failedTx.insert(iter);
diff --git a/src/miner.h b/src/miner.h
index bc4da63da..9fab55611 100644
--- a/src/miner.h
+++ b/src/miner.h
@@ -192,8 +192,11 @@ private:
     void onlyUnconfirmed(CTxMemPool::setEntries& testSet);
     /** Test if a new package would "fit" in the block */
     bool TestPackage(uint64_t packageSize, int64_t packageSigOpsCost);
-    /** Test if a set of transactions are all final */
-    bool TestPackageFinalityAndSerializedSize(const CTxMemPool::setEntries& package);
+    /** Perform checks on each transaction in a package:
+      * locktime, premature-witness, serialized size (if necessary)
+      * These checks should always succeed, and they're here
+      * only as an extra check in case of suboptimal node configuration */
+    bool TestPackageTransactions(const CTxMemPool::setEntries& package);
     /** Return true if given transaction from mapTx has already been evaluated,
       * or if the transaction's cached data in mapTx is incorrect. */
     bool SkipMapTxEntry(CTxMemPool::txiter it, indexed_modified_transaction_set &mapModifiedTx, CTxMemPool::setEntries &failedTx);