diff --git a/src/sentinel.c b/src/sentinel.c
index 227fb69386..a5ce31ee8f 100644
--- a/src/sentinel.c
+++ b/src/sentinel.c
@@ -36,6 +36,7 @@
 #include <ctype.h>
 #include <arpa/inet.h>
 #include <sys/socket.h>
+#include <sys/wait.h>
 
 extern char **environ;