BIND-9 Logging

[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 ?