diff --git a/src/vm.c b/src/vm.c
index a3a9e90b7..d615b064f 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -255,7 +255,7 @@ top_proc(mrb_state *mrb, const struct RProc *proc)
 
 #define CI_PROC_SET(ci, p) do {\
   ci->proc = p;\
-  ci->pc = (p && !MRB_PROC_CFUNC_P(p)) ? p->body.irep->iseq : NULL;\
+  ci->pc = (p && !MRB_PROC_CFUNC_P(p) && p->body.irep) ? p->body.irep->iseq : NULL;\
 } while (0)
 
 void