2.9 engine thermostat gasket?

[oldgeebee]

When I took the thermostat housing off there was no paper gasket in sight but wasn't leaking. The thermostat has a rubber sealing ring around its top flange which looks as though it would form a seal. However, now it's all back together it looks like there is a slight drip from the bottom of the thermostat housing. The exploded diagram of the 2.9 engine doesn't show any paper gasket but does shown the rubber sealing ring.
Should there be a paper gasket as well as the rubber seal? If not, what's the secret to getting the thermostat housing to seal?
TIA

[oldgeebee]

OK, thanks guys!
I'd cleaned up all the seating surfaces but didn't use any silicone grease - will give that a go. . .