diff --git a/src/backend/utils/cache/relfilenodemap.c b/src/backend/utils/cache/relfilenodemap.c
index 56d7c73d33..5a5cf853bd 100644
--- a/src/backend/utils/cache/relfilenodemap.c
+++ b/src/backend/utils/cache/relfilenodemap.c
@@ -146,6 +146,9 @@ RelidByRelfilenode(Oid reltablespace, Oid relfilenode)
 	ScanKeyData skey[2];
 	Oid			relid;
 
+	if (!OidIsValid(relfilenode))
+		return InvalidOid;
+
 	if (RelfilenodeMapHash == NULL)
 		InitializeRelfilenodeMap();