I’d like to use on_query_completions to add some custom completions to the list.

If I

return (u'hello', u'hello'), ...]

it gets added to the list, but if I

return (u'?hello', u'?hello'), ...]

it overrides the whole list.

To be more precise, as soon as a special character is returned, the whole list is overwritten. Is this a bug? How can I work around it?