Decay channel for new particle

I am using G4PhaseSpaceDecayChannel() class to add a decay mode to a new particle I already defined.
my example G4PhaseSpaceDecayChannel(“ps”,1.00,3," gamma"," gamma"," gamma")
the problem is the sum of energies of the gamma emitted is more than the parent mass !!! which is not making sence of course.
any idea why?