diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index 9fcd12020ae..0ccfb3a20a4 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -4445,24 +4445,41 @@ ExpireTreeKnownAssignedTransactionIds(TransactionId xid, int nsubxids,
 
 /*
  * ExpireAllKnownAssignedTransactionIds
- *		Remove all entries in KnownAssignedXids
+ *		Remove all entries in KnownAssignedXids and reset lastOverflowedXid.
  */
 void
 ExpireAllKnownAssignedTransactionIds(void)
 {
 	LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
 	KnownAssignedXidsRemovePreceding(InvalidTransactionId);
+
+	/*
+	 * Reset lastOverflowedXid.  Currently, lastOverflowedXid has no use after
+	 * the call of this function.  But do this for unification with what
+	 * ExpireOldKnownAssignedTransactionIds() do.
+	 */
+	procArray->lastOverflowedXid = InvalidTransactionId;
 	LWLockRelease(ProcArrayLock);
 }
 
 /*
  * ExpireOldKnownAssignedTransactionIds
- *		Remove KnownAssignedXids entries preceding the given XID
+ *		Remove KnownAssignedXids entries preceding the given XID and
+ *		potentially reset lastOverflowedXid.
  */
 void
 ExpireOldKnownAssignedTransactionIds(TransactionId xid)
 {
 	LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
+
+	/*
+	 * Reset lastOverflowedXid if we know all transactions that have been
+	 * possibly running are being gone.  Not doing so could cause an incorrect
+	 * lastOverflowedXid value, which makes extra snapshots be marked as
+	 * suboverflowed.
+	 */
+	if (TransactionIdPrecedes(procArray->lastOverflowedXid, xid))
+		procArray->lastOverflowedXid = InvalidTransactionId;
 	KnownAssignedXidsRemovePreceding(xid);
 	LWLockRelease(ProcArrayLock);
 }