diff --git a/audit.c b/audit.c
index 091361560..33a04376d 100644
--- a/audit.c
+++ b/audit.c
@@ -26,6 +26,7 @@
 
 #include <stdarg.h>
 #include <string.h>
+#include <unistd.h>
 
 #ifdef SSH_AUDIT_EVENTS