Hash#transform_keys's fix is backported to Ruby 2.5.1
Hash#transform_keys's fix is backported to Ruby 2.5.1

https://bugs.ruby-lang.org/issues/14380

ruby/spec,ruby/spec,eregon/rubyspec,eregon/rubyspec,ruby/spec,ruby/rubyspec,eregon/rubyspec,nobu/rubyspec,nobu/rubyspec,nobu/rubyspec,ruby/rubyspec