diff --git a/simgear/nasal/cppbind/detail/nasal_traits.hxx b/simgear/nasal/cppbind/detail/nasal_traits.hxx
index 73306936..26767d76 100644
--- a/simgear/nasal/cppbind/detail/nasal_traits.hxx
+++ b/simgear/nasal/cppbind/detail/nasal_traits.hxx
@@ -43,6 +43,9 @@ namespace osg
   template<class T> class ref_ptr;
   template<class T> class observer_ptr;
 
+  template<class T, class Y>
+  ref_ptr<T> static_pointer_cast(const ref_ptr<Y>&);
+
   class Vec2b;
   class Vec2d;
   class Vec2f;