hook_helo_parse working?

[crayon]

I'm trying to write a plugin that uses hook_helo_parse but am not having 
any success. Some debugging shows my function gets called, it returns a 
CODE ref, but the ref'd sub never gets called here's a simple example:

sub hook_helo_parse {
   my $self = shift;
   my $ref = \&parser;
   $self->qp->log(LOGALERT, "hook_helo_parse called and returning $ref");
   return(OK, $ref);
}
sub parser {
   my( $self, $cmd, $line) = @_;
   $self->qp->log(LOGALERT, "helo parser called for $cmd and $line");
   return(OK, $line);
}

When run I see the first alert, but not the second- does anyone else 
have a plugin using this hook that's working? I'm using qpsmtpd-0.40 and 
the async server if that makes any difference.