Index: unix/utils/subprocess_waiter.c
--- unix/utils/subprocess_waiter.c.orig
+++ unix/utils/subprocess_waiter.c
@@ -8,8 +8,9 @@
 #include "putty.h"
 #include "tree234.h"
 
-#include <unistd.h>
 #include <sys/wait.h>
+#include <unistd.h>
+#include <signal.h>
 
 struct SubprocessWaiter {
     pid_t pid;
