fontconfig: updating give " invalid cache file"

[sean darcy]

....................
   Updating  : fontconfig 
####################### [11/50]
/var/cache/fontconfig: invalid cache file: 
3830d5c3ddfd5cd38a049b759396e72e-x86.cache-2
/var/cache/fontconfig: invalid cache file: 
beeeeb3dfe132a8a0633a017c99ce0c0-x86.cache-2
/var/cache/fontconfig: invalid cache file: 
53c7585a07a08fda4ab40d9e1c024bb8-x86.cache-2
/var/cache/fontconfig: invalid cache file: 
e19de935dec46bbf3ed114ee4965548a-x86.cache-2
/var/cache/fontconfig: invalid cache file: 
e3ead4b767b8819993a6fa3ae306afa9-x86.cache-2
......................

What this? A bug, or have I corrupted the cache files somehow?

sean