diff --git a/protocol.cpp b/protocol.cpp
index 40e4941..163af9c 100644
--- a/protocol.cpp
+++ b/protocol.cpp
@@ -7,6 +7,7 @@
 #include <string>
 #include <map>
 #include <vector>
+#include <sys/select.h>
 
 #include "defines.h"
 #include "error.h"