fix ave/spatial and changing box size along a different dimension

Dear all,

I'm trying to run a simulation with changing box size along one
dimension only (z), and I would like to use fix ave/spatial with units
box along another dimension (y). However I get the following error
(I'm using the 5 Apr 2014 version):

ERROR: Fix ave/spatial settings invalid with changing box size

Do you think it would it be possible to relax the condition in
fix_ave_spatial.cpp, and test that the box size is not changing only
in the binned dimension(s)?

Best regards,