diff --git a/owlps-positioner/src/outputnetworksocket.cc b/owlps-positioner/src/outputnetworksocket.cc
index b8d1183..5952a2a 100644
--- a/owlps-positioner/src/outputnetworksocket.cc
+++ b/owlps-positioner/src/outputnetworksocket.cc
@@ -11,6 +11,7 @@
 #include "posexcept.hh"
 
 #include <cstdio> // For perror()
+#include <unistd.h> // For close()
 
 using namespace std ;