diff --git a/libc/include/sys/stat.h b/libc/include/sys/stat.h
index 0d350e0..775fb08 100644
--- a/libc/include/sys/stat.h
+++ b/libc/include/sys/stat.h
@@ -163,6 +163,7 @@
 
 #if defined(__BIONIC_FORTIFY)
 
+#if __ANDROID_API__ >= 18
 __BIONIC_FORTIFY_INLINE
 mode_t umask(mode_t mode) {
 #if !defined(__clang__)
@@ -175,6 +176,8 @@
 #endif
   return __umask_chk(mode);
 }
+#endif /* __ANDROID_API__ >= 18 */
+
 #endif /* defined(__BIONIC_FORTIFY) */
 
 #if __ANDROID_API__ >= 21