diff --git a/src/backend/nodes/list.c b/src/backend/nodes/list.c
index 75aa5baa80..90f93e893c 100644
--- a/src/backend/nodes/list.c
+++ b/src/backend/nodes/list.c
@@ -1553,11 +1553,11 @@ list_copy_head(const List *oldlist, int len)
 {
 	List	   *newlist;
 
-	len = Min(oldlist->length, len);
-
-	if (len <= 0)
+	if (oldlist == NIL || len <= 0)
 		return NIL;
 
+	len = Min(oldlist->length, len);
+
 	newlist = new_list(oldlist->type, len);
 	memcpy(newlist->elements, oldlist->elements, len * sizeof(ListCell));