diff --git a/udp-listener.h b/udp-listener.h
index fc65a17..06536e6 100644
--- a/udp-listener.h
+++ b/udp-listener.h
@@ -1,5 +1,11 @@
+#ifndef UDPLISTENER_H
+#define UDPLISTENER_H
 
 /* UDP listener: upon incoming packet, find where it should go
  * This is run in its own process and never returns.
  */
 void udp_listener(struct listen_endpoint* endpoint, int num_endpoints, int active_endpoint);
+
+
+
+#endif /* UDPLISTENER_H */