diff --git a/src/main.cpp b/src/main.cpp
index b8b9bc35..d3589144 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -471,38 +471,53 @@ unsigned int LimitOrphanTxSize(unsigned int nMaxOrphans)
 
 
 
-bool IsStandardTx(const CTransaction& tx)
+bool IsStandardTx(const CTransaction& tx, string& reason)
 {
-    if (tx.nVersion > CTransaction::CURRENT_VERSION)
+    if (tx.nVersion > CTransaction::CURRENT_VERSION) {
+        reason = "version";
         return false;
+    }
 
-    if (!IsFinalTx(tx))
+    if (!IsFinalTx(tx)) {
+        reason = "non-final";
         return false;
+    }
 
     // Extremely large transactions with lots of inputs can cost the network
     // almost as much to process as they cost the sender in fees, because
     // computing signature hashes is O(ninputs*txsize). Limiting transactions
     // to MAX_STANDARD_TX_SIZE mitigates CPU exhaustion attacks.
     unsigned int sz = tx.GetSerializeSize(SER_NETWORK, CTransaction::CURRENT_VERSION);
-    if (sz >= MAX_STANDARD_TX_SIZE)
+    if (sz >= MAX_STANDARD_TX_SIZE) {
+        reason = "tx-size";
         return false;
+    }
 
     BOOST_FOREACH(const CTxIn& txin, tx.vin)
     {
         // Biggest 'standard' txin is a 3-signature 3-of-3 CHECKMULTISIG
         // pay-to-script-hash, which is 3 ~80-byte signatures, 3
         // ~65-byte public keys, plus a few script ops.
-        if (txin.scriptSig.size() > 500)
+        if (txin.scriptSig.size() > 500) {
+            reason = "scriptsig-size";
             return false;
-        if (!txin.scriptSig.IsPushOnly())
+        }
+        if (!txin.scriptSig.IsPushOnly()) {
+            reason = "scriptsig-not-pushonly";
             return false;
+        }
     }
     BOOST_FOREACH(const CTxOut& txout, tx.vout) {
-        if (!::IsStandard(txout.scriptPubKey))
+        if (!::IsStandard(txout.scriptPubKey)) {
+            reason = "scriptpubkey";
             return false;
-        if (txout.IsDust(CTransaction::nMinRelayTxFee))
+        }
+        if (txout.IsDust(CTransaction::nMinRelayTxFee)) {
+            reason = "dust";
             return false;
+        }
     }
+
     return true;
 }
 
@@ -796,8 +811,10 @@ bool CTxMemPool::accept(CValidationState &state, CTransaction &tx, bool fLimitFr
         return error("CTxMemPool::accept() : not accepting nLockTime beyond 2038 yet");
 
     // Rather not work on nonstandard transactions (unless -testnet)
-    if (!TestNet() && !IsStandardTx(tx))
-        return error("CTxMemPool::accept() : nonstandard transaction type");
+    string reason;
+    if (!TestNet() && !IsStandardTx(tx, reason))
+        return error("CTxMemPool::accept() : nonstandard transaction: %s",
+                     reason.c_str());
 
     // is it already in the memory pool?
     uint256 hash = tx.GetHash();
diff --git a/src/main.h b/src/main.h
index 7b77b0e3..8ad2437c 100644
--- a/src/main.h
+++ b/src/main.h
@@ -326,7 +326,7 @@ bool CheckTransaction(const CTransaction& tx, CValidationState& state);
 /** Check for standard transaction types
     @return True if all outputs (scriptPubKeys) use only standard transaction forms
 */
-bool IsStandardTx(const CTransaction& tx);
+bool IsStandardTx(const CTransaction& tx, std::string& reason);
 
 bool IsFinalTx(const CTransaction &tx, int nBlockHeight = 0, int64 nBlockTime = 0);
 
diff --git a/src/test/script_P2SH_tests.cpp b/src/test/script_P2SH_tests.cpp
index 23cb3a8e..3c666d28 100644
--- a/src/test/script_P2SH_tests.cpp
+++ b/src/test/script_P2SH_tests.cpp
@@ -74,6 +74,7 @@ BOOST_AUTO_TEST_CASE(sign)
     }
 
     CTransaction txFrom;  // Funding transaction:
+    string reason;
     txFrom.vout.resize(8);
     for (int i = 0; i < 4; i++)
     {
@@ -82,7 +83,7 @@ BOOST_AUTO_TEST_CASE(sign)
         txFrom.vout[i+4].scriptPubKey = standardScripts[i];
         txFrom.vout[i+4].nValue = COIN;
     }
-    BOOST_CHECK(IsStandardTx(txFrom));
+    BOOST_CHECK(IsStandardTx(txFrom, reason));
 
     CTransaction txTo[8]; // Spending transactions
     for (int i = 0; i < 8; i++)
@@ -167,13 +168,14 @@ BOOST_AUTO_TEST_CASE(set)
     }
 
     CTransaction txFrom;  // Funding transaction:
+    string reason;
     txFrom.vout.resize(4);
     for (int i = 0; i < 4; i++)
     {
         txFrom.vout[i].scriptPubKey = outer[i];
         txFrom.vout[i].nValue = CENT;
     }
-    BOOST_CHECK(IsStandardTx(txFrom));
+    BOOST_CHECK(IsStandardTx(txFrom, reason));
 
     CTransaction txTo[4]; // Spending transactions
     for (int i = 0; i < 4; i++)
@@ -189,7 +191,7 @@ BOOST_AUTO_TEST_CASE(set)
     for (int i = 0; i < 4; i++)
     {
         BOOST_CHECK_MESSAGE(SignSignature(keystore, txFrom, txTo[i], 0), strprintf("SignSignature %d", i));
-        BOOST_CHECK_MESSAGE(IsStandardTx(txTo[i]), strprintf("txTo[%d].IsStandard", i));
+        BOOST_CHECK_MESSAGE(IsStandardTx(txTo[i], reason), strprintf("txTo[%d].IsStandard", i));
     }
 }
 
diff --git a/src/test/transaction_tests.cpp b/src/test/transaction_tests.cpp
index 53d1307b..0c7475b4 100644
--- a/src/test/transaction_tests.cpp
+++ b/src/test/transaction_tests.cpp
@@ -260,16 +260,17 @@ BOOST_AUTO_TEST_CASE(test_IsStandard)
     key.MakeNewKey(true);
     t.vout[0].scriptPubKey.SetDestination(key.GetPubKey().GetID());
 
-    BOOST_CHECK(IsStandardTx(t));
+    string reason;
+    BOOST_CHECK(IsStandardTx(t, reason));
 
     t.vout[0].nValue = 5011; // dust
-    BOOST_CHECK(!IsStandardTx(t));
+    BOOST_CHECK(!IsStandardTx(t, reason));
 
     t.vout[0].nValue = 6011; // not dust
-    BOOST_CHECK(IsStandardTx(t));
+    BOOST_CHECK(IsStandardTx(t, reason));
 
     t.vout[0].scriptPubKey = CScript() << OP_1;
-    BOOST_CHECK(!IsStandardTx(t));
+    BOOST_CHECK(!IsStandardTx(t, reason));
 }
 
 BOOST_AUTO_TEST_SUITE_END()