diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index d90cb9a902..e16d8ef212 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -443,6 +443,12 @@ expand_vacuum_rel(VacuumRelation *vrel)
 		Form_pg_class classForm;
 		bool		include_parts;
 
+		/*
+		 * Since autovacuum workers supply OIDs when calling vacuum(), no
+		 * autovacuum worker should reach this code.
+		 */
+		Assert(!IsAutoVacuumWorkerProcess());
+
 		/*
 		 * We transiently take AccessShareLock to protect the syscache lookup
 		 * below, as well as find_all_inheritors's expectation that the caller