diff --git a/src/vm.c b/src/vm.c
index 298c5d178..190601279 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -375,7 +375,6 @@ mrb_env_unshare(mrb_state *mrb, struct REnv *e, mrb_bool noraise)
   if (e == NULL) return TRUE;
   if (!MRB_ENV_ONSTACK_P(e)) return TRUE;
   if (e->cxt != mrb->c) return TRUE;
-  if (e == CI_ENV(mrb->c->cibase)) return TRUE; /* for mirb */
 
   e->cxt = NULL; /* make possible to GC the fiber that generated the env */