diff --git a/include/mruby/proc.h b/include/mruby/proc.h
index def00628f..33018003c 100644
--- a/include/mruby/proc.h
+++ b/include/mruby/proc.h
@@ -86,6 +86,8 @@ struct RProc {
 #define MRB_PROC_SCOPE_P(p) (((p)->flags & MRB_PROC_SCOPE) != 0)
 #define MRB_PROC_NOARG 4096 /* for MRB_PROC_CFUNC_FL, it would be something like MRB_ARGS_NONE() or MRB_METHOD_NOARG_FL */
 #define MRB_PROC_NOARG_P(p) (((p)->flags & MRB_PROC_NOARG) != 0)
+#define MRB_PROC_ALIAS 8192
+#define MRB_PROC_ALIAS_P(p) (((p)->flags & MRB_PROC_ALIAS) != 0)
 
 #define mrb_proc_ptr(v)    ((struct RProc*)(mrb_ptr(v)))
 
diff --git a/src/class.c b/src/class.c
index 05e54e2e2..27cfddca8 100644
--- a/src/class.c
+++ b/src/class.c
@@ -2266,7 +2266,7 @@ mrb_alias_method(mrb_state *mrb, struct RClass *c, mrb_sym a, mrb_sym b)
         mrb_field_write_barrier(mrb, (struct RBasic*)e, (struct RBasic*)tc);
       }
       p->e.env = e;
-      p->flags |= MRB_PROC_ENVSET;
+      p->flags |= MRB_PROC_ENVSET | MRB_PROC_ALIAS;
       mrb_field_write_barrier(mrb, (struct RBasic*)p, (struct RBasic*)e);
     }
   }
diff --git a/src/vm.c b/src/vm.c
index b504fdcc9..28fdfde7f 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -1918,7 +1918,7 @@ RETRY_TRY_BLOCK:
       struct RClass* target_class = CI_TARGET_CLASS(ci);
 
       mid = ci->mid;
-      if (MRB_PROC_ENV_P(p) && p->e.env->mid && p->e.env->mid != mid) { /* alias support */
+      if (MRB_PROC_ALIAS_P(p) && MRB_PROC_ENV_P(p) && p->e.env->mid && p->e.env->mid != mid) { /* alias support */
         mid = p->e.env->mid;    /* restore old mid */
       }