negative_ttl & squid 3.1

[Calvin Park <carrot@xxxxxxxxxxxx>]

Hello squid users~

I am using  on squid 3.1.4 , and I need to cache about 404 code.

In squid 2.7 , there have rule like "refresh_pattern .    0       20%
   4320 negative_ttl=xxx"

When can I use negative_ttl syntax  in squid 3.1 ?

Thanks.