diff --git a/sandbox-darwin.c b/sandbox-darwin.c
index 35f0c4d1a..a61de7495 100644
--- a/sandbox-darwin.c
+++ b/sandbox-darwin.c
@@ -31,6 +31,7 @@
 
 #include "log.h"
 #include "sandbox.h"
+#include "monitor.h"
 #include "xmalloc.h"
 
 /* Darwin/OS X sandbox */