WatchGroup required for this OFPGT_FF

[md-sal-binding-commit-0] ERROR o.o.o.o.m.c.s.c.GroupConvertor - WatchGroup required for this OFPGT_FF

I start to getting this messages every time I want to set a new group.
Accordingly with OF1.3 specification:
"The watch_port and watch_group fields are only required for fast failover groups, and may be optionally implemented for other group types. These fields indicate the port and/or group whose liveness controls whether this bucket is a candidate for forwarding."

The group is not mandatory in case is set a port. In my case I had set a port but not a group.