diff --git a/owlps-positioner/src/inputudpsocket.cc b/owlps-positioner/src/inputudpsocket.cc
index 0439f34..e1d7070 100644
--- a/owlps-positioner/src/inputudpsocket.cc
+++ b/owlps-positioner/src/inputudpsocket.cc
@@ -48,6 +48,7 @@
 
 #include <iostream>
 #include <cstdio> // For perror()
+#include <unistd.h> // For close()
 #include <arpa/inet.h> // For inet_ntop()
 #include <boost/tr1/unordered_map.hpp>