diff --git a/vm_eval.c b/vm_eval.c
index 807f322854..b0cdc7aefe 100644
--- a/vm_eval.c
+++ b/vm_eval.c
@@ -1771,6 +1771,7 @@ pm_eval_make_iseq(VALUE src, VALUE fname, int line,
     pm_scope_node_t *prev = result.node.previous;
     while (prev) {
         pm_scope_node_t *next = prev->previous;
+        pm_constant_id_list_free(&prev->locals);
         ruby_xfree(prev);
         prev = next;
     }