Localizing in 1.6.4?

[ezres]

Hey, I've made my first mod, and I'd like to ask a question.

 

I've read in a page, that loading from en_US.lang which is in the assets/modname/lang folder, is done by using I18N.getString("name.of.text"), which should produce "test", if the lang file contains "name.of.text=test". However, it's not working for me. I'm trying to display this text in a GUI, by adding a centered string to it, but nothing appears. Do I have to register my lang files anywhere in an initialization event? I'm already loading a block's name from it and it's working like a charm, but not with GUI elements.

 

Here's how I try it in the initGui method:

this.buttonList.add(this.done = new GuiButton(0,this.width/2 - 110, this.height/4+30,90,20,I18N.getString("testgui.okbutton")));

 

And I have 2 lang files, an english and a hungarian. Both of them contains "testgui.okbutton=OK", but neither of them loads - yes, I tried to change language ingame to see if that's the problem, but still no luck.

[ezres]

The server is running on 1.6.4, because some mods we are using are not being updated to 1.7 or above, so I have to stick at 1.6.4.