quasseclient --hidewindow does not hide window when automatically started

Steps to reproduce starting quasselclient on login

$ kcmshell5 autostart
Add Program > choose quasselclient > command 'quasselclient --hidewindow'

Log off and start a new session.
Quassel Client will start, but also show its window

Expected:
The same behaviour when as when started from the command line with the --hidewindow option. In that case, quasselclient will start hidden.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: quassel-client 0.12.2-0ubuntu0.1
ProcVersionSignature: Ubuntu 3.19.0-25.26-generic 3.19.8-ckt2
Uname: Linux 3.19.0-25-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.17.2-0ubuntu1.2
Architecture: amd64
CurrentDesktop: KDE
Date: Mon Aug 17 21:07:59 2015
InstallationDate: Installed on 2015-08-12 (5 days ago)
InstallationMedia: Kubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
SourcePackage: quassel
UpgradeStatus: No upgrade log present (probably fresh install)