Devhelp shows its window buttons twice if maximized

The Devhelp windows has the close, minimize, maximize buttons two times if it is maximized. One set in Unitys top panel and a second set in Devhelps CSD.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: devhelp 3.14.0-1
ProcVersionSignature: Ubuntu 3.19.0-15.15-generic 3.19.3
Uname: Linux 3.19.0-15-generic i686
ApportVersion: 2.17.2-0ubuntu1
Architecture: i386
CurrentDesktop: Unity
Date: Sat Apr 25 09:35:05 2015
ExecutablePath: /usr/bin/devhelp
InstallationDate: Installed on 2014-01-27 (453 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release i386 (20131016.1)
ProcEnviron:
 LANGUAGE=de_DE
 PATH=(custom, user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: devhelp
UpgradeStatus: Upgraded to vivid on 2015-04-24 (0 days ago)