diff --git a/explicit_bzero.c b/explicit_bzero.c
index 592e700..d681a27 100644
--- a/explicit_bzero.c
+++ b/explicit_bzero.c
@@ -5,6 +5,7 @@
  * Written by Ted Unangst
  */
 
+#define __STDC_WANT_LIB_EXT1__ 1
 #include <string.h>
 
 /*