1 files changed, 1 insertions, 1 deletions
diff --git a/session.h b/session.h
index ba945149..2b6ac79d 100644
--- a/session.h
+++ b/session.h
@@ -167,7 +167,7 @@ struct systemtap_session
   unsigned num_errors () { return seen_errors.size(); }
   // void print_error (const parse_error& e);
   void print_error (const semantic_error& e);
-  void print_warning (std::string w);
+  void print_warning (const std::string& w);
 
   // reNB: new POD members likely need to be explicitly cleared in the ctor.
 };