diff --git a/simgear/nasal/cppbind/cppbind_fwd.hxx b/simgear/nasal/cppbind/cppbind_fwd.hxx
index c57b8fbb..4f122fba 100644
--- a/simgear/nasal/cppbind/cppbind_fwd.hxx
+++ b/simgear/nasal/cppbind/cppbind_fwd.hxx
@@ -27,6 +27,8 @@
 namespace nasal
 {
 
+  class bad_nasal_cast;
+
   class CallContext;
   class Context;
   class ContextWrapper;
diff --git a/simgear/nasal/cppbind/detail/from_nasal_helper.hxx b/simgear/nasal/cppbind/detail/from_nasal_helper.hxx
index 9eee0690..436dcb3c 100644
--- a/simgear/nasal/cppbind/detail/from_nasal_helper.hxx
+++ b/simgear/nasal/cppbind/detail/from_nasal_helper.hxx
@@ -43,8 +43,6 @@ class SGPath;
 
 namespace nasal
 {
-  class Hash;
-  class String;
 
   /**
    * Thrown when converting a type from/to Nasal has failed
diff --git a/simgear/nasal/cppbind/detail/to_nasal_helper.hxx b/simgear/nasal/cppbind/detail/to_nasal_helper.hxx
index f34d9fb6..7d54fcb6 100644
--- a/simgear/nasal/cppbind/detail/to_nasal_helper.hxx
+++ b/simgear/nasal/cppbind/detail/to_nasal_helper.hxx
@@ -24,7 +24,7 @@
 
 #include <simgear/math/SGMath.hxx>
 #include <simgear/math/SGRect.hxx>
-#include <simgear/nasal/nasal.h>
+#include <simgear/nasal/cppbind/cppbind_fwd.hxx>
 
 #include <boost/function/function_fwd.hpp>
 #include <boost/utility/enable_if.hpp>
@@ -40,8 +40,6 @@ class SGPath;
 
 namespace nasal
 {
-  class CallContext;
-  class Hash;
 
   typedef boost::function<naRef (CallContext)> free_function_t;