diff --git a/simgear/scene/util/SGPickCallback.hxx b/simgear/scene/util/SGPickCallback.hxx
index 6361d20a..23bc747d 100644
--- a/simgear/scene/util/SGPickCallback.hxx
+++ b/simgear/scene/util/SGPickCallback.hxx
@@ -22,6 +22,8 @@
 #ifndef SG_SCENE_PICKCALLBACK_HXX
 #define SG_SCENE_PICKCALLBACK_HXX
 
+#include <osg/Vec2d>
+   
 #include <simgear/structure/SGReferenced.hxx>
 #include <simgear/structure/SGSharedPtr.hxx>
 #include <simgear/math/SGMath.hxx>