diff --git a/libc/include/sys/linux-unistd.h b/libc/include/sys/linux-unistd.h
index ae9077f..f060374 100644
--- a/libc/include/sys/linux-unistd.h
+++ b/libc/include/sys/linux-unistd.h
@@ -20,6 +20,7 @@
 uid_t            getresuid (void);
 gid_t            getresgid (void);
 pid_t            gettid (void);
+ssize_t          readahead (int, off64_t, size_t);
 int              getgroups (int, gid_t *);
 pid_t            getpgid (pid_t);
 pid_t            getppid (void);