diff --git a/ModFile.cc b/ModFile.cc
index 134d9982..52f7f856 100644
--- a/ModFile.cc
+++ b/ModFile.cc
@@ -217,7 +217,7 @@ ModFile::writeOutputFiles(const string &basename, bool clear_all) const
       it != statements.end(); it++)
     (*it)->writeOutput(mOutputFile, basename);
 
-  mOutputFile << "save('" << basename << "_results.mat', 'oo_');" << endl;
+  mOutputFile << "save('" << basename << "_results.mat', 'oo_', 'M_');" << endl;
   mOutputFile << "diary off" << endl;
   mOutputFile << "rmpath " << basename << ";\n";