Not sure why this is missing, but okay.
--- a/includes.h.orig
+++ b/includes.h
@@ -38,6 +38,7 @@
 #include <sys/un.h>
 #include <sys/wait.h>
 #include <sys/resource.h>
+#include <sys/select.h>
 
 #include <stdio.h>
 #include <errno.h>