Plotting broken in C++ coloring demo

I'm getting the error below when running the C++ coloring demo. This is not detected by the buildbot because it's the plotting that fails, while the demo has exit value 0.

buildbot@buildmaster:cpp$ ./demo_coloring
Coloring mesh.
Start Boost coloring.
Boost coloring finished.
Number of colors: 30
Plotting f (unnamed MeshFunction), press 'q' to continue...
Coloring mesh.
terminate called after throwing an instance of 'std::runtime_error'
  what(): *** Error: MeshFunction file of type 'uint', expected 'double'.
[buildmaster:25641] *** Process received signal ***
[buildmaster:25641] Signal: Aborted (6)
[buildmaster:25641] Signal code: (-6)
[buildmaster:25641] [ 0] [0xb78a240c]
[buildmaster:25641] [ 1] /lib/libc.so.6(abort+0x182) [0xb756ae42]
[buildmaster:25641] [ 2] /usr/lib/libstdc++.so.6(_ZN9__gnu_cxx27__verbose_terminate_handlerEv+0x155) [0xb6e73055]
[buildmaster:25641] [ 3] /usr/lib/libstdc++.so.6(+0xabf35) [0xb6e70f35]
[buildmaster:25641] [ 4] /usr/lib/libstdc++.so.6(+0xabf72) [0xb6e70f72]
[buildmaster:25641] [ 5] /usr/lib/libstdc++.so.6(+0xac0e1) [0xb6e710e1]
[buildmaster:25641] [ 6] /home/buildbot/buildbots/main/fenics-build/dolfin/dolfin/libdolfin.so.0(_ZNK6dolfin6Logger5errorESs+0x272) [0xb0074a0e]
[buildmaster:25641] [ 7] /home/buildbot/buildbots/main/fenics-build/dolfin/dolfin/libdolfin.so.0(_ZN6dolfin5errorESsz+0x24d) [0xb007d101]
[buildmaster:25641] [ 8] /home/buildbot/buildbots/main/fenics-build/dolfin/dolfin/libdolfin.so.0(_ZN6dolfin15XMLMeshFunction19start_mesh_functionEPKhPS2_+0x830) [0xafe7ac98]
[buildmaster:25641] [ 9] /home/buildbot/buildbots/main/fenics-build/dolfin/dolfin/libdolfin.so.0(_ZN6dolfin15XMLMeshFunction13start_elementEPKhPS2_+0xc0) [0xafe78940]
[buildmaster:25641] [10] /home/buildbot/buildbots/main/fenics-build/dolfin/dolfin/libdolfin.so.0(_ZN6dolfin7XMLFile13start_elementEPKhPS2_+0x7a) [0xafe9567a]
[buildmaster:25641] [11] /home/buildbot/buildbots/main/fenics-build/dolfin/dolfin/libdolfin.so.0(_ZN6dolfin17sax_start_elementEPvPKhPS2_+0x49) [0xafe95aea]
[buildmaster:25641] [12] /usr/lib/libxml2.so.2(xmlParseStartTag+0x468) [0xb2015318]
[buildmaster:25641] [13] /usr/lib/libxml2.so.2(xmlParseElement+0x250) [0xb2015660]
[buildmaster:25641] [14] /usr/lib/libxml2.so.2(xmlParseContent+0x15a) [0xb2015a2a]
[buildmaster:25641] [15] /usr/lib/libxml2.so.2(xmlParseElement+0x12c) [0xb201553c]
[buildmaster:25641] [16] /usr/lib/libxml2.so.2(xmlParseDocument+0x2a2) [0xb201c952]
[buildmaster:25641] [17] /usr/lib/libxml2.so.2(xmlSAXUserParseFile+0x6d) [0xb201d6bd]
[buildmaster:25641] [18] /home/buildbot/buildbots/main/fenics-build/dolfin/dolfin/libdolfin.so.0(_ZN6dolfin7XMLFile5parseEv+0x77) [0xafe953b9]
[buildmaster:25641] [19] /home/buildbot/buildbots/main/fenics-build/dolfin/dolfin/libdolfin.so.0(_ZN6dolfin7XMLFile8read_xmlINS_12MeshFunctionIdEEEEvRT_+0x10c) [0xafe99da6]
[buildmaster:25641] [20] /home/buildbot/buildbots/main/fenics-build/dolfin/dolfin/libdolfin.so.0(_ZN6dolfin7XMLFilersERNS_12MeshFunctionIdEE+0x42) [0xafe97036]
[buildmaster:25641] [21] /home/buildbot/buildbots/main/fenics/lib/python2.6/site-packages/dolfin/_cpp.so(_ZN6dolfin4FilersINS_12MeshFunctionIdEEEEvRT_+0xc1) [0xb0e5d7eb]
[buildmaster:25641] [22] /home/buildbot/buildbots/main/fenics/lib/python2.6/site-packages/dolfin/_cpp.so(+0x50a6f5) [0xb0daf6f5]
[buildmaster:25641] [23] /home/buildbot/buildbots/main/fenics/lib/python2.6/site-packages/dolfin/_cpp.so(+0x50c1f5) [0xb0db11f5]
[buildmaster:25641] [24] /usr/bin/python(PyObject_Call+0x4a) [0x805fd6a]
[buildmaster:25641] [25] /usr/bin/python() [0x8067d5c]
[buildmaster:25641] [26] /usr/bin/python(PyObject_Call+0x4a) [0x805fd6a]
[buildmaster:25641] [27] /usr/bin/python() [0x80b01ef]
[buildmaster:25641] [28] /usr/bin/python() [0x80b0d8d]
[buildmaster:25641] [29] /usr/bin/python() [0x806030e]
[buildmaster:25641] *** End of error message ***