drush verbose without command: Undefined index: is_alias

When typing drush without a trailing command in combination with the verbose option,
set by -v
or
$options['v'] = 1; in drushrc.php
i got

Undefined index:  is_alias                                                                     [notice]

These lines appear between Commands: and the list of command with aliases and description.

While investigating this, i temporarily removed all drush contribs.
The sum of these lines above is 34, which is the number of commands / lines of output below Commands: without breaks).