diff --git a/include/mruby/internal.h b/include/mruby/internal.h
index 05d7b9a26..5abd648dd 100644
--- a/include/mruby/internal.h
+++ b/include/mruby/internal.h
@@ -80,8 +80,7 @@ void mrb_gc_free_mt(mrb_state*, struct RClass*);
 
 /* hash */
 size_t mrb_hash_memsize(mrb_value obj);
-void mrb_gc_mark_hash(mrb_state*, struct RHash*);
-size_t mrb_gc_mark_hash_size(mrb_state*, struct RHash*);
+size_t mrb_gc_mark_hash(mrb_state*, struct RHash*);
 void mrb_gc_free_hash(mrb_state*, struct RHash*);
 
 /* irep */
diff --git a/src/gc.c b/src/gc.c
index 839213e70..818892049 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -675,8 +675,7 @@ gc_mark_children(mrb_state *mrb, mrb_gc *gc, struct RBasic *obj)
 
   case MRB_TT_HASH:
     children += mrb_gc_mark_iv(mrb, (struct RObject*)obj);
-    mrb_gc_mark_hash(mrb, (struct RHash*)obj);
-    children += mrb_gc_mark_hash_size(mrb, (struct RHash*)obj);
+    children += mrb_gc_mark_hash(mrb, (struct RHash*)obj);
     break;
 
   case MRB_TT_STRING:
diff --git a/src/hash.c b/src/hash.c
index 1aa12f6e8..dcfc7dff1 100644
--- a/src/hash.c
+++ b/src/hash.c
@@ -1072,18 +1072,13 @@ h_replace(mrb_state *mrb, struct RHash *h, struct RHash *orig_h)
   }
 }
 
-void
+size_t
 mrb_gc_mark_hash(mrb_state *mrb, struct RHash *h)
 {
   h_each(h, entry, {
     mrb_gc_mark_value(mrb, entry->key);
     mrb_gc_mark_value(mrb, entry->val);
   });
-}
-
-size_t
-mrb_gc_mark_hash_size(mrb_state *mrb, struct RHash *h)
-{
   return h_size(h) * 2;
 }