diff --git a/src/backend/executor/execPartition.c b/src/backend/executor/execPartition.c
index 1fa4d84c42..6a170eea03 100644
--- a/src/backend/executor/execPartition.c
+++ b/src/backend/executor/execPartition.c
@@ -1589,6 +1589,9 @@ adjust_partition_tlist(List *tlist, TupleConversionMap *map)
 	AttrMap    *attrMap = map->attrMap;
 	AttrNumber	attrno;
 
+	if (tlist == NIL)
+		return NIL;
+
 	Assert(tupdesc->natts == attrMap->maplen);
 	for (attrno = 1; attrno <= tupdesc->natts; attrno++)
 	{