diff --git a/simgear/io/socktest.cxx b/simgear/io/socktest.cxx
index 2586b42c..1cd8f79f 100644
--- a/simgear/io/socktest.cxx
+++ b/simgear/io/socktest.cxx
@@ -1,3 +1,7 @@
+#ifdef HAVE_CONFIG_H
+#  include <simgear_config.h>
+#endif
+
 #include <simgear/compiler.h>
 
 #include <unistd.h>