diff --git a/src/rviz/visualizer_app.cpp b/src/rviz/visualizer_app.cpp
index 2646cd19ac..88c4e51980 100644
--- a/src/rviz/visualizer_app.cpp
+++ b/src/rviz/visualizer_app.cpp
@@ -159,6 +159,13 @@ bool VisualizerApp::init( int argc, char** argv )
       if (vm.count("display-config"))
       {
         display_config = vm["display-config"].as<std::string>();
+        if( display_config.substr( display_config.size() - 4, 4 ) == ".vcg" )
+        {
+          std::cerr << "ERROR: the config file '" << display_config << "' is a .vcg file, which is the old rviz config format." << std::endl;
+          std::cerr << "       New config files have a .rviz extension and use YAML formatting.  The format changed" << std::endl;
+          std::cerr << "       between Fuerte and Groovy.  There is not (yet) an automated conversion program." << std::endl;
+          return false;
+        }
       }
 
       if (vm.count("splash-screen"))