diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c
index 462b1a9636..e29efa1023 100644
--- a/src/backend/utils/cache/relcache.c
+++ b/src/backend/utils/cache/relcache.c
@@ -313,7 +313,7 @@ ScanPgRelation(Oid targetRelId, bool indexOK, bool force_non_historic)
 	Relation	pg_class_desc;
 	SysScanDesc pg_class_scan;
 	ScanKeyData key[1];
-	Snapshot	snapshot;
+	Snapshot	snapshot = NULL;
 
 	/*
 	 * If something goes wrong during backend startup, we might find ourselves
@@ -343,12 +343,12 @@ ScanPgRelation(Oid targetRelId, bool indexOK, bool force_non_historic)
 	/*
 	 * The caller might need a tuple that's newer than the one the historic
 	 * snapshot; currently the only case requiring to do so is looking up the
-	 * relfilenode of non mapped system relations during decoding.
+	 * relfilenode of non mapped system relations during decoding. That
+	 * snapshot cant't change in the midst of a relcache build, so there's no
+	 * need to register the snapshot.
 	 */
 	if (force_non_historic)
 		snapshot = GetNonHistoricCatalogSnapshot(RelationRelationId);
-	else
-		snapshot = GetCatalogSnapshot(RelationRelationId);
 
 	pg_class_scan = systable_beginscan(pg_class_desc, ClassOidIndexId,
 									   indexOK && criticalRelcachesBuilt,