diff --git a/src/vm.c b/src/vm.c
index 236d33a12..f13945d9a 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -253,6 +253,7 @@ cipop(mrb_state *mrb)
       stack_copy(p, e->stack, len);
     }
     e->stack = p;
+    mrb_write_barrier(mrb, (struct RBasic *)e);
   }
 
   c->ci--;