diff --git a/src/SerializedLedger.cpp b/src/SerializedLedger.cpp
index acc58da3c..1e29a99c2 100644
--- a/src/SerializedLedger.cpp
+++ b/src/SerializedLedger.cpp
@@ -98,10 +98,12 @@ bool SerializedLedgerEntry::thread(const uint256& txID, uint32 ledgerSeq, uint25
 	uint256 oldPrevTxID = getFieldH256(sfLastTxnID);
 	Log(lsTRACE) << "Thread Tx:" << txID << " prev:" << oldPrevTxID;
 	if (oldPrevTxID == txID)
+	{ // this transaction is already threaded
+		assert(getFieldU32(sfLastTxnSeq) == ledgerSeq);
 		return false;
+	}
 	prevTxID = oldPrevTxID;
 	prevLedgerID = getFieldU32(sfLastTxnSeq);
-	assert(prevTxID != txID);
 	setFieldH256(sfLastTxnID, txID);
 	setFieldU32(sfLastTxnSeq, ledgerSeq);
 	return true;