diff --git a/libc/netbsd/net/reentrant.h b/libc/netbsd/net/reentrant.h
index 15507eb..60bff08 100644
--- a/libc/netbsd/net/reentrant.h
+++ b/libc/netbsd/net/reentrant.h
@@ -102,6 +102,7 @@
 
 #include <pthread.h>
 #include <signal.h>
+#include <sys/cdefs.h>
 
 #define	mutex_t			pthread_mutex_t
 #define	MUTEX_INITIALIZER	PTHREAD_MUTEX_INITIALIZER