Whistle Leaks?

I am an new whistle player. Today I received my Low D Pennywhistle made by T&G. When I play the whistle, saliva leaks through the seam of the mouthpiece. Is this normal or is my whistle defective? It seems that if saliva comes through the seam, that it must be leaking air, which would lower the quality of sound. Should I return this whistle for a new one?
Any advice will be appreciated

Giles

Doh, send it back.