diff --git a/src/backend/storage/lmgr/predicate.c b/src/backend/storage/lmgr/predicate.c
index f0c8ee4..134a0a0 100644
--- a/src/backend/storage/lmgr/predicate.c
+++ b/src/backend/storage/lmgr/predicate.c
@@ -1184,6 +1184,7 @@ InitPredicateLocks(void)
 		}
 		PredXact->OldCommittedSxact = CreatePredXact();
 		SetInvalidVirtualTransactionId(PredXact->OldCommittedSxact->vxid);
+		PredXact->OldCommittedSxact->prepareSeqNo = 0;
 		PredXact->OldCommittedSxact->commitSeqNo = 0;
 		PredXact->OldCommittedSxact->SeqNo.lastCommitBeforeSnapshot = 0;
 		SHMQueueInit(&PredXact->OldCommittedSxact->outConflicts);
@@ -1644,6 +1645,7 @@ RegisterSerializableTransactionInt(Snapshot snapshot)
 	/* Initialize the structure. */
 	sxact->vxid = vxid;
 	sxact->SeqNo.lastCommitBeforeSnapshot = PredXact->LastSxactCommitSeqNo;
+	sxact->prepareSeqNo = InvalidSerCommitSeqNo;
 	sxact->commitSeqNo = InvalidSerCommitSeqNo;
 	SHMQueueInit(&(sxact->outConflicts));
 	SHMQueueInit(&(sxact->inConflicts));
@@ -4401,18 +4403,13 @@ OnConflict_CheckForSerializationFailure(const SERIALIZABLEXACT *reader,
 		{
 			SERIALIZABLEXACT *t2 = conflict->sxactIn;
 
-			/*
-			 * Note that if T2 is merely prepared but not yet committed, we
-			 * rely on t->commitSeqNo being InvalidSerCommitSeqNo, which is
-			 * larger than any valid commit sequence number.
-			 */
 			if (SxactIsPrepared(t2)
 				&& (!SxactIsCommitted(reader)
-					|| t2->commitSeqNo <= reader->commitSeqNo)
+					|| t2->prepareSeqNo <= reader->commitSeqNo)
 				&& (!SxactIsCommitted(writer)
-					|| t2->commitSeqNo <= writer->commitSeqNo)
+					|| t2->prepareSeqNo <= writer->commitSeqNo)
 				&& (!SxactIsReadOnly(reader)
-			   || t2->commitSeqNo <= reader->SeqNo.lastCommitBeforeSnapshot))
+			   || t2->prepareSeqNo <= reader->SeqNo.lastCommitBeforeSnapshot))
 			{
 				failure = true;
 				break;
@@ -4453,17 +4450,11 @@ OnConflict_CheckForSerializationFailure(const SERIALIZABLEXACT *reader,
 		{
 			SERIALIZABLEXACT *t0 = conflict->sxactOut;
 
-			/*
-			 * Note that if the writer is merely prepared but not yet
-			 * committed, we rely on writer->commitSeqNo being
-			 * InvalidSerCommitSeqNo, which is larger than any valid commit
-			 * sequence number.
-			 */
 			if (!SxactIsDoomed(t0)
 				&& (!SxactIsCommitted(t0)
-					|| t0->commitSeqNo >= writer->commitSeqNo)
+					|| t0->commitSeqNo >= writer->prepareSeqNo)
 				&& (!SxactIsReadOnly(t0)
-			   || t0->SeqNo.lastCommitBeforeSnapshot >= writer->commitSeqNo))
+			   || t0->SeqNo.lastCommitBeforeSnapshot >= writer->prepareSeqNo))
 			{
 				failure = true;
 				break;
@@ -4602,6 +4593,7 @@ PreCommit_CheckForSerializationFailure(void)
 						 offsetof(RWConflictData, inLink));
 	}
 
+	MySerializableXact->prepareSeqNo = ++(PredXact->LastSxactCommitSeqNo);
 	MySerializableXact->flags |= SXACT_FLAG_PREPARED;
 
 	LWLockRelease(SerializableXactHashLock);
@@ -4776,6 +4768,7 @@ predicatelock_twophase_recover(TransactionId xid, uint16 info,
 		sxact->pid = 0;
 
 		/* a prepared xact hasn't committed yet */
+		sxact->prepareSeqNo = RecoverySerCommitSeqNo;
 		sxact->commitSeqNo = InvalidSerCommitSeqNo;
 		sxact->finishedBefore = InvalidTransactionId;
 
diff --git a/src/include/storage/predicate_internals.h b/src/include/storage/predicate_internals.h
index 0c90f27..43fcce4 100644
--- a/src/include/storage/predicate_internals.h
+++ b/src/include/storage/predicate_internals.h
@@ -57,6 +57,7 @@ typedef struct SERIALIZABLEXACT
 {
 	VirtualTransactionId vxid;	/* The executing process always has one of
 								 * these. */
+	SerCommitSeqNo prepareSeqNo;
 	SerCommitSeqNo commitSeqNo;
 	union						/* these values are not both interesting at
 								 * the same time */