diff --git a/mrbgems/mruby-hash-ext/test/hash.rb b/mrbgems/mruby-hash-ext/test/hash.rb
index 04324665b..5c08212ce 100644
--- a/mrbgems/mruby-hash-ext/test/hash.rb
+++ b/mrbgems/mruby-hash-ext/test/hash.rb
@@ -255,12 +255,6 @@ assert("Hash#dig") do
   assert_nil(h.dig(:d))
 end
 
-assert("Hash#transform_keys") do
-  h = {a:{b:{c:1}}}
-  assert_equal(1, h.dig(:a, :b, :c))
-  assert_nil(h.dig(:d))
-end
-
 assert("Hash#transform_keys") do
   h = {"1" => 100, "2" => 200}
   assert_equal(h.transform_keys{|k| k+"!"},