Problem with range requests on squid

[spies]

I have squid set up to cache windows updates and on the whole it works well, that is until a partial request happens and then it misses the cache, I'm running 3.1.20 do I need a newer package in order for partial requests to work correctly?

This is in my squid.inc file

refresh_pattern ([^.]+\.)?(download|(windows)?update)\.(microsoft\.)?com/.*\.(cab|exe|msi|msp|psf|esd) 4320 100% 43200 reload-into-ims; range_offset_limit -1;

[spies]

Anyone? I work in an IT shop so a lot of our traffic are updates, it would be great if the 206 requests were pulled out of the cache rather than across the internet.