diff --git a/libc/bionic/__strlen_chk.cpp b/libc/bionic/__strlen_chk.cpp
index 6621a6a..a67e15e 100644
--- a/libc/bionic/__strlen_chk.cpp
+++ b/libc/bionic/__strlen_chk.cpp
@@ -26,6 +26,8 @@
  * SUCH DAMAGE.
  */
 
+#undef _FORTIFY_SOURCE
+
 #include <string.h>
 #include <stdlib.h>
 #include "private/libc_logging.h"