OOP:Sirius/Padfoot/Snuffles being 'outed'

[tcyhunt]

No: HPFGUIDX 66795

"Because the Ministry of Magic's still after me, and Voldemort will 
know all about me being an Animagus by now, Wormtail will have told 
him, so my big disguise is useless."

Sirius says this to Harry in Ch. 5 of OotP.  The question it raises 
for me is why wouldn't Wormtail have told LV long ago that Sirius was 
an Animagus (as well as James and that Lupin's a warewolf)?  Wormtail 
has been in league with the bad guys since before the Potter's were 
killed...why would he have just recently told LV?

Tcy