For multi-dimension Hash, .merge will replace the values as a 2 dimension hash.

>> {"number" => {"1" => "one","2" => "two"}}.merge({"number" => {"3" => "three"}})
=> {"number"=>{"3"=>"three"}}

We needed the keep the hash values and merge complex hash together that is loaded from YAML.

Solution?

class Hash
    def recursive_merge(h)
        self.merge!(h) {|key, _old, _new| if _old.class == Hash then _old.recursive_merge(_new) else _new end  }
    end
end

>>{"number" => {"1" => "one","2" => "two"}}.recursive_merge({"number" => {"3" => "three"}})
=> {"number"=>{"1"=>"one", "2"=>"two", "3"=>"three"}}