why segfault when parameter is not "int" and is "unsigned long long int"

[Fran <prog1@xxxxxxxxxxxxx>]

> typedef unsigned long long int UID;
> ...
>                   UID us;
>                     usuario = va_arg (ap, UID);
> printf("%llu",us);
> 
segfault

This code  works if I put "unsigned int" but do not with "unsigned long long int".

Should work I think.