diff --git a/src/Main/FGManipulator.cxx b/src/Main/FGManipulator.cxx
index e4a551f5d..4b797e6ae 100644
--- a/src/Main/FGManipulator.cxx
+++ b/src/Main/FGManipulator.cxx
@@ -1,7 +1,8 @@
+#ifdef HAVE_CONFIG_H
+#  include <config.h>
+#endif
 #include <osg/Math>
-
 #include <osgViewer/Viewer>
-
 #include <plib/pu.h>
 #include "FGManipulator.hxx"