Switching language removes autocompleted part from address bar

Firefox Development
#1

Reproduction steps

  1. Have at least two input languages.
  2. Start typing some URL in the address bar that you know is going to be autocompleted.
  3. Press right arrow to accept the autocompletion. The cursor is now at the end of the URL and you are ready to type the rest of it.
  4. Switch language.

What happens?

The previously autocompleted part is erased.

What was expected?

The autocompleted part should not be erased since it was confirmed by pressing the right arrow (step 3).