No English language to select in Sandbox if English is not the default langauge

Steps to reproduce:

• make wiki multi-language e.g. with "fr de en" as supported languages, and 'en'; not as the default language
• go to the Sandbox.WebHome, see that 'English' is still the current default, and pick any other langauge
• see the Sandbox page in the other langage.

so far evertything is as expected. However if one wants to switch back to English, this is not avaliable as an option in the language drop down.
Also if one navigates to the (single language) Sandbox.TestPage1 is shows the page in English (which is ok, of course) but claims it to be in the current language (which is currently something different).

This is an UI issue with the language switch, as manually appending ?language=en switches the language successfully. It seems only the "language" field and not the "defaultLanguage" of the document is taken into account.