@@ -12345,8 +12362,15 @@ test_if_skip_sort_order(JOIN_TAB *tab,OR
           KEYUSE *keyuse= tab->keyuse;
           while (keyuse->key != new_ref_key && keyuse->table == tab->table)
             keyuse++;
+         /*
+           We will now create the ref access method for the new key,
+           and we know that another key was being used until now, so
+           we know that key will be in the set tab->key_dependent. Therefore
+           we don't need to send the whole set of previous tables in the plan
+           to create_ref_for_key, as we would normally have to.
+         */
           if (create_ref_for_key(tab->join, tab, keyuse,
-                                 tab->join->const_table_map))
+                                 tab->join->key_dependent))
             DBUG_RETURN(0);
        }
        else