Comment 44 for bug 1164023

Ok, so the MM_06 branch in git is actually free of your problem. Your issue is fixed (99% chance :)) in the following commit:
http://cgit.freedesktop.org/ModemManager/ModemManager/commit/?h=MM_06&id=5d854a32cf2d04cbdb3d16f019d277caaba69ab4

So, either compile directly that branch, or ask Ubuntu packagers to also include that commit in the build.