synaptic runs wrong dpkg command to show installed files for i386 packages on multiarch

I installed libglu1-mesa-dev:i386 on an amd64 platform. dpkg shows the i386 files are installed:

$ dpkg -L libglu1-mesa-dev:i386
...
/usr/lib/i386-linux-gnu/libGLU.a
/usr/lib/i386-linux-gnu/libGLU.so

and it shows that the amd64 version is not installed (it conflicts):

$ dpkg -L libglu1-mesa-dev
Package `libglu1-mesa-dev' is not installed.

However, if I select libglu1-mesa-dev:i386 in Synaptic and select Properties / Installed Files, it tells me that the package is not installed, so it must be checking libglu1-mesa-dev instead of libglu1-mesa-dev:i386.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: synaptic 0.75.5~exp6
Uname: Linux 3.3.0-rc5-git-20120226.0832 x86_64
ApportVersion: 1.94-0ubuntu1
Architecture: amd64
Date: Sun Mar 4 08:47:25 2012
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
ProcEnviron:
 LANGUAGE=en_AU:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_AU.UTF-8
 SHELL=/bin/bash
SourcePackage: synaptic
UpgradeStatus: Upgraded to precise on 2012-03-02 (1 days ago)