no piety produced with holy mosque

[dworfi]

hello, i have a bug i think, i built a mosque in a country and upgrade it to holy mosque (exact term? not sur i have french version) but when i clic on the town it said that no piety is produced in the town (i have "-" under piety symbol). in the piety menu, there is no production from holy mosque. The province is orthdox and my religion is muslim, i check the manual but nowhere it said a province with a different religion than the country produc no piety. Bug or rules?

[Refardeon]

rules...

realms that do not share your kingdoms religion dont give you piety... convert the realm and the holy mosque will give you endless piety ;)