BGP Route Filter Problem

I have the following router filter on my router:

chain=asprepend_in prefix=122.0.0.0 prefix-length=8-32 invert-match=no action=passthrough set-bgp-local-pref=110

Why does this match 122.0.0.0/24 but not 122.197.127.0/17? How can I match anything falling inside 122.0.0.0/8?

Thanks,

Keefe

chain=asprepend_in prefix=122.0.0.0**/8** prefix-length=8-32 invert-match=no action=passthrough set-bgp-local-pref=110