PHP Fatal error: Class 'Sabre\VObject\Property\Text' not found

[hede]

Hi list,

I cannot read mail in roundcube:

[24-Jun-2016 21:16:54 Europe/Berlin] PHP Fatal error:  Class
'Sabre\VObject\Property\Text' not found
in /usr/share/roundcubemail/plugins/libcalendaring/libvcalendar.php on
line 1386

all kolab packages compiled from:

http://obs.kolabsys.com:82/Kolab:/Winterfell/Debian_8.0/

like: roundcubemail-plugins-kolab_3.3~dev20160313-0~kolab1.dsc

It seems there's no Sabre\VObject at all. The one included in Debian 8 is to old for roundcubemail-plugin-libcalendaring (2.1.5 vs. 3.3.3). And those php-composer-thingy seems not to do what it has to do. Any hints? 

Regards
hede