diff --git a/libc/include/sys/linux-unistd.h b/libc/include/sys/linux-unistd.h
index 7494efe..5e9c2f0 100644
--- a/libc/include/sys/linux-unistd.h
+++ b/libc/include/sys/linux-unistd.h
@@ -85,6 +85,7 @@
 int              ftruncate (int, off_t);
 int              getdents (unsigned int, struct dirent *, unsigned int);
 int              fsync (int);
+int              fdatasync (int);
 int              fchown (int, uid_t, gid_t);
 void             sync (void);
 int              __fcntl64 (int, int, void *);