Languages and HTML editor

htmlarea doesn't work with languages other than "registered" (I mean: available by default), e.g. https://xwiki/xwiki/bin/edit/Main/WebHome?language=pl&xpage=htmlarea opens "regular" editor with html source, instead of WYSIWYG editor. Changing 'pl' to 'en' in url opens HTML editor. How can I fix it? -- "First they ignore you. Then they laugh at you. Then they fight you. Then you win." - Mohandas Gandhi.