FuseFS for ruby gives me the wrong gid and uid

I am using the FuseFS ruby gem to create a custom filesystem in ruby 1.8. the only problem is, that while I am in the write_to method of my custom filesystem class the开发者_如何转开发 FuseFS.uid method only gives me 0 while it should return the valid uid of the accessing user. In other methods it works fine and returns for example 4832 (the user id). Why is that so and how can I change this behavior?