CLI autocompletion issue

In a freshly extracted Karaf 4.1.2, running on JDK9, hitting TAB just moves the blinking cursor.
No autocompletion is triggered.

If I start typing any command instead, like pressing a single j and then hit TAB, I get the correct suggestion.

I suspect this is either a bug or the help message at boot should be changed from:

  Apache Karaf (4.1.2)

Hit '<tab>' for a list of available commands