diff --git a/src/main.cpp b/src/main.cpp
index 89761dc2b3..4b2c32e345 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -466,7 +466,7 @@ unsigned int LimitOrphanTxSize(unsigned int nMaxOrphans)
 
 bool IsStandardTx(const CTransaction& tx, string& reason)
 {
-    if (tx.nVersion > CTransaction::CURRENT_VERSION) {
+    if (tx.nVersion > CTransaction::CURRENT_VERSION || tx.nVersion < 1) {
         reason = "version";
         return false;
     }
@@ -1778,6 +1778,11 @@ bool DisconnectBlock(CBlock& block, CValidationState& state, CBlockIndex* pindex
         CCoins &outs = view.GetCoins(hash);
 
         CCoins outsBlock = CCoins(tx, pindex->nHeight);
+        // The CCoins serialization does not serialize negative numbers.
+        // No network rules currently depend on the version here, so an inconsistency is harmless
+        // but it must be corrected before txout nversion ever influences a network rule.
+        if (outsBlock.nVersion < 0)
+            outs.nVersion = outsBlock.nVersion;
         if (outs != outsBlock)
             fClean = fClean && error("DisconnectBlock() : added transaction mismatch? database corrupted");