diff --git a/libc/stdlib/atexit.h b/libc/stdlib/atexit.h
index 39df2e1..4b3e5ab 100644
--- a/libc/stdlib/atexit.h
+++ b/libc/stdlib/atexit.h
@@ -30,6 +30,8 @@
  *
  */
 
+#include <sys/cdefs.h>
+
 struct atexit {
 	struct atexit *next;		/* next in list */
 	int ind;			/* next index in this table */