Bit odd that as most Honda cars have the sensor rigged to go off only if the vehicle is actually moving.
It would seem odd for it it trigger stationary as the seatbelt is not required. Reason they have the alarm is to tell you that you are moving with no belt fastened.
Also, the alarm should stop the moment you clip the belt in so if it's only until you start moving then is it a huge issue?
So either it is when you are moving that you ain't wearing the belt or you have a fault in the sensor (which may also affect your airbag system) in which case I would suggest getting it looked at.