diff --git a/libc/include/fcntl.h b/libc/include/fcntl.h
index 6e2ad51..74ea523 100644
--- a/libc/include/fcntl.h
+++ b/libc/include/fcntl.h
@@ -86,6 +86,10 @@
 extern int posix_fadvise64(int, off64_t, off64_t, int);
 extern int posix_fallocate64(int, off64_t, off64_t);
 
+#if defined(__USE_GNU)
+ssize_t readahead(int, off64_t, size_t);
+#endif
+
 extern int __open_2(const char*, int);
 extern int __open_real(const char*, int, ...) __RENAME(open);
 extern int __openat_2(int, const char*, int);