extern int read_cow_header(int (*reader)(__u64, char *, int, void *),
                           void *arg, __u32 *version_out,
                           char **backing_file_out, time_t *mtime_out,
-                          __u64 *size_out, int *sectorsize_out,
+                          unsigned long long *size_out, int *sectorsize_out,
                           __u32 *align_out, int *bitmap_offset_out);
 
 extern int write_cow_header(char *cow_file, int fd, char *backing_file,
 
        return(os_seek_file(fd, offset));
 }
 
-static inline int cow_file_size(char *file, __u64 *size_out)
+static inline int cow_file_size(char *file, unsigned long long *size_out)
 {
        return(os_file_size(file, size_out));
 }