Dialpad does not accept touchscreen input

I am using empathy to make VOIP calls to a conference call system. I am trying to use my touchscreen to enter numbers in the dialpad, but that does not work. Using the mouse to enter numbers in the dialpad works just fine.

To reproduce:
1) Start a new VOIP call (Ctrl-M); make a call (I am dialed into a conference line)
2) In the call window, click the dialpad button to show the dialpad
3) Use the touchscreen to enter numbers in the dialpad

Expected results:
Using the touchscreen to enter numbers in the dialpad works: pressing a number on the dialpad results in the number being displayed in the small text field above the dialpad

Actual results:
Using the touchscreen to enter numbers in the dialpad does not work. The dialpad buttons depress as if the button was being pressed, but the numbers are not entered in the small text field above the dialpad

Using the mouse to click buttons in the dialpad works just fine for me. The touchscreen itself is working fine on this machine.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: empathy 3.8.6-0ubuntu7
ProcVersionSignature: Ubuntu 3.13.0-19.39-generic 3.13.6
Uname: Linux 3.13.0-19-generic x86_64
ApportVersion: 2.13.3-0ubuntu1
Architecture: amd64
CurrentDesktop: Unity
Date: Tue Mar 25 20:58:36 2014
DistributionChannelDescriptor:
 # This is a distribution channel descriptor
 # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
 canonical-oem-somerville-precise-amd64-20130203-1
EcryptfsInUse: Yes
InstallationDate: Installed on 2013-12-02 (113 days ago)
InstallationMedia: Ubuntu 12.04 "Precise" - Build amd64 LIVE Binary 20130203-13:50
SourcePackage: empathy
UpgradeStatus: Upgraded to trusty on 2014-02-12 (41 days ago)