diff --git a/auth-bsdauth.c b/auth-bsdauth.c
index f718e5d..37d527d 100644
--- a/auth-bsdauth.c
+++ b/auth-bsdauth.c
@@ -27,6 +27,8 @@
 
 #include <sys/types.h>
 
+#include <stdarg.h>
+
 #ifdef BSD_AUTH
 #include "xmalloc.h"
 #include "key.h"