diff --git a/libc/include/sys/ttydefaults.h b/libc/include/sys/ttydefaults.h
index b62aab1..62af84b 100644
--- a/libc/include/sys/ttydefaults.h
+++ b/libc/include/sys/ttydefaults.h
@@ -42,6 +42,8 @@
 #ifndef _SYS_TTYDEFAULTS_H_
 #define	_SYS_TTYDEFAULTS_H_
 
+#include <sys/cdefs.h>
+
 /*
  * Defaults on "first" open.
  */