BIND-9 Logging Rollover

[DJ]

How do I get BIND-9 to roll-over a log file to a new version when it
exceeds
a certain size ? e.g I have

channel named_log
                 {
                       file "/named.log" versions 3 size 1M;
                         severity info;
                        print-time yes;
                        print-category yes;
                        print-severity yes;

                };
 ....

 but all it seems to do is to stop writing to named.log when it gets to 1M.
 Can I get BIND-9 to rollover to a new file automatically ?