diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 7982e16..6ba545a 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1792,6 +1792,12 @@ PrescanPreparedTransactions(TransactionId **xids_p, int *nxids_p)
 	int			allocsize = 0;
 	int			i;
 
+	/*
+	 * Set result and maxsubxid to the largest XID known to us.
+	 */
+	TransactionIdRetreat(result);
+	TransactionIdRetreat(maxsubxid);
+
 	LWLockAcquire(TwoPhaseStateLock, LW_SHARED);
 	for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
 	{