diff --git a/simgear/io/sg_socket.cxx b/simgear/io/sg_socket.cxx
index e642639a..70bb382c 100644
--- a/simgear/io/sg_socket.cxx
+++ b/simgear/io/sg_socket.cxx
@@ -28,6 +28,8 @@
 #include <strings.h>
 #endif
 
+#include <ostream>
+
 #include <simgear/debug/logstream.hxx>
 
 #include "sg_socket.hxx"