(acroread-en:26300): Gtk-WARNING **: /usr/lib/gtk-2.0/2.10.0/engines/libclearlooks.so: wrong ELF class: ELFCLASS64

Today I started looking at this annoying warning everytime I start acroread:

$ acroread ./medical/dicom/2008/08_02pu.pdf
(acroread-en:26300): Gtk-WARNING **: /usr/lib/gtk-2.0/2.10.0/engines/libclearlooks.so: wrong ELF class: ELFCLASS64

Looking in the bug tracker it seems this is:

* http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=490947

But as reported here, this is a recent regression:

* http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=544324#15

I could not figure out how this lib is actually being pulled in.