diff --git a/src/branch2.cpp b/src/branch2.cpp
index 11f1c01c..89b60974 100644
--- a/src/branch2.cpp
+++ b/src/branch2.cpp
@@ -18,7 +18,7 @@ Branch2::Branch2()
 
 }
 
-Branch2::Branch2(Branch2 &v_)
+Branch2::Branch2(Branch2 const &v_)
   : enabled(v_.enabled),
     mode(v_.mode),
     min_free_space(v_.min_free_space),