Always display first completion

With prompt_toolkit 1 it was possible to return multiple completions and always first completion was selected. After update to PT2, this isn't possible. When I try to complete with TAB key, only partial completion is used (only "msg" string) and second TAB should be pressed to full completion. Can I somehow emulate PT1 behaviour? Here is my example code:

from prompt_toolkit import prompt
from prompt_toolkit.completion import Completer, Completion

class MyCustomCompleter(Completer):
    def get_completions(self, document, complete_event):
        yield Completion('msg test', start_position=0)
        yield Completion('msg help', start_position=0)

text1 = prompt(">> ",
  completer=MyCustomCompleter(),
  complete_while_typing=True,
  reserve_space_for_menu=0
)
print("RESULT:", repr(text1))

I need after first TAB to see "msg test" in prompt.

Start with the MyCustomCompleter.get_completions example and the prompt call using prompt_toolkit 2. Run it and inspect how the first TAB handles the two yielded Completion objects. Done means the first TAB inserts the full "msg test" completion, matching the reported prompt_toolkit 1 behavior.