diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index b85a666..0cbe2c9 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -350,6 +350,7 @@ MarkAsPreparing(TransactionId xid, const char *gid,
 		gxact = TwoPhaseState->prepXacts[i];
 		if (strcmp(gxact->gid, gid) == 0)
 		{
+			LWLockRelease(TwoPhaseStateLock);
 			ereport(ERROR,
 					(errcode(ERRCODE_DUPLICATE_OBJECT),
 					 errmsg("transaction identifier \"%s\" is already in use",
@@ -359,11 +360,14 @@ MarkAsPreparing(TransactionId xid, const char *gid,
 
 	/* Get a free gxact from the freelist */
 	if (TwoPhaseState->freeGXacts == NULL)
+	{
+		LWLockRelease(TwoPhaseStateLock);
 		ereport(ERROR,
 				(errcode(ERRCODE_OUT_OF_MEMORY),
 				 errmsg("maximum number of prepared transactions reached"),
 				 errhint("Increase max_prepared_transactions (currently %d).",
 						 max_prepared_xacts)));
+	}
 	gxact = TwoPhaseState->freeGXacts;
 	TwoPhaseState->freeGXacts = gxact->next;