Thanks Sterl, you're right, this was because I have don´t compiled with the -threaded flag, this works fine now.

> This answer may be way off base, but if differences appear between 
> ghci and compiled versions, I've often found its as simple as 
> remembering to compile with the -threaded flag. The ghci runtime is 
> threaded by default, as I understand it, while compiled binaries are 
> not, and IO operations will block in very different fashions (i.e. in
> their own thread, or stalling the entire app) depending on the runtime.

> Regards,
> sterl.
Alvaro