diff --git a/include/mruby/hash.h b/include/mruby/hash.h
index 2026c8e0d..449a7d4bc 100644
--- a/include/mruby/hash.h
+++ b/include/mruby/hash.h
@@ -25,6 +25,7 @@ struct RHash {
 #define mrb_hash_value(p)  mrb_obj_value((void*)(p))
 
 MRB_API mrb_value mrb_hash_new_capa(mrb_state*, mrb_int);
+MRB_API mrb_value mrb_ensure_hash_type(mrb_state *mrb, mrb_value hash);
 MRB_API mrb_value mrb_check_hash_type(mrb_state *mrb, mrb_value hash);
 
 /*
diff --git a/src/hash.c b/src/hash.c
index 122f5b5d5..7d81bc343 100644
--- a/src/hash.c
+++ b/src/hash.c
@@ -320,6 +320,12 @@ mrb_hash_set(mrb_state *mrb, mrb_value hash, mrb_value key, mrb_value val)
   return;
 }
 
+MRB_API mrb_value
+mrb_ensure_hash_type(mrb_state *mrb, mrb_value hash)
+{
+  return mrb_convert_type(mrb, hash, MRB_TT_HASH, "Hash", "to_hash");
+}
+
 MRB_API mrb_value
 mrb_check_hash_type(mrb_state *mrb, mrb_value hash)
 {
@@ -959,7 +965,7 @@ mrb_hash_merge(mrb_state *mrb, mrb_value hash1, mrb_value hash2)
   khiter_t k;
 
   mrb_hash_modify(mrb, hash1);
-  hash2 = mrb_check_hash_type(mrb, hash2);
+  hash2 = mrb_ensure_hash_type(mrb, hash2);
   h1 = RHASH_TBL(hash1);
   h2 = RHASH_TBL(hash2);