diff --git a/src/osgPlugins/iv/parser.hpp b/src/osgPlugins/iv/parser.hpp
index b094be336..1f5f4ad1e 100644
--- a/src/osgPlugins/iv/parser.hpp
+++ b/src/osgPlugins/iv/parser.hpp
@@ -1,7 +1,7 @@
 #ifndef BISON_PARSER_HPP
 # define BISON_PARSER_HPP
 
-//#ifndef YYSTYPE
+#ifndef YYSTYPE
 typedef union {
   char *s_value;
   float f_value;
@@ -13,10 +13,11 @@ typedef union {
   PolygonList *plist;
   Matrix matrix;
   int i_value;
-} YYSTYPE;
-//# define YYSTYPE yystype
-//# define YYSTYPE_IS_TRIVIAL 1
-//#endif
+} yystype;
+# define YYSTYPE yystype
+# define YYSTYPE_IS_TRIVIAL 1
+#endif
+
 # define	STRING	257
 # define	QUOTED_STRING	258
 # define	FLOAT	259