diff --git a/lib/mrb/mrb_table_sort_key.c b/lib/mrb/mrb_table_sort_key.c
index 46aea9839b..860dd2b476 100644
--- a/lib/mrb/mrb_table_sort_key.c
+++ b/lib/mrb/mrb_table_sort_key.c
@@ -32,12 +32,18 @@
 static void
 mrb_grn_table_sort_key_free(mrb_state *mrb, void *data)
 {
+  grn_ctx *ctx = (grn_ctx *)mrb->ud;
   grn_table_sort_key *sort_key = data;
 
   if (!sort_key) {
     return;
   }
 
+  if (sort_key->key) {
+    if (sort_key->key->header.type == GRN_ACCESSOR) {
+      grn_obj_unlink(ctx, sort_key->key);
+    }
+  }
   mrb_free(mrb, sort_key);
 }