diff --git a/src/osgPlugins/osg/XmlStreamOperator.h b/src/osgPlugins/osg/XmlStreamOperator.h
index 93e8b2257..33bb50f7a 100644
--- a/src/osgPlugins/osg/XmlStreamOperator.h
+++ b/src/osgPlugins/osg/XmlStreamOperator.h
@@ -482,7 +482,8 @@ public:
 
     virtual bool matchString( const std::string& str )
     {
-        prepareStream();
+        if (!prepareStream()) return false;
+
         std::string strInStream = osgDB::trimEnclosingSpaces(_sstream.str());
         if ( strInStream==str )
         {