FYI everybody, the law of Qatar makes no difference between muslim and non-muslim employees in this matter; according to the Emir's decree a few years ago, working more than six hours a day during Ramadan is ILLEGAL for all, unless it's a life and death situation.
There are many private companies who do not follow the law and invent restrictions such as the idea that only Muslims are allowed to have shorter hours.
You could always complain to the Labour Dept (if you think it's worth it).