graphical corruption of left toolbar with text enabled

By default, the left toolbar in Kolourpaint has only icons, no text.

Right-clicking it and changing the Text Position option to any setting other than Icons Only, the background of the toolbar and buttons gets totally corrupted, but the program is still usable.

This is on Ubuntu Desktop with Unity, not Kubuntu, in case that matters.

Reproduced with nouveau and nvidia, on 12.04 (Unity and Unity-2D) and 14.04 (Unity only), 32-bit and 64-bit.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: kolourpaint4 4:4.13.0-0ubuntu1
ProcVersionSignature: Ubuntu 3.13.0-24.46-generic 3.13.9
Uname: Linux 3.13.0-24-generic x86_64
ApportVersion: 2.14.1-0ubuntu3
Architecture: amd64
CasperVersion: 1.340
CurrentDesktop: Unity
Date: Thu May 15 20:30:02 2014
LiveMediaBuild: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: kolourpaint
UpgradeStatus: No upgrade log present (probably fresh install)