When did ZFS support snapshotting during a scrub?

[Darren Pilgrim]

The other day I discovered that my 8.3-R systems (zpool v28, ZFS v4) 
will let me create and destroy snapshots when a scrub is running.  This 
was not the case in $previous_version, but a quick scan of release notes 
doesn't mention it.  I believe you couldn't snapshot during a scrub in 
8.1-R, but I'm not sure.  Does anyone know which ZFS/zpool version 
removed this restriction?