diff --git a/src/tgba/futurecondcol.cc b/src/tgba/futurecondcol.cc
index 019eff8b3..57a163876 100644
--- a/src/tgba/futurecondcol.cc
+++ b/src/tgba/futurecondcol.cc
@@ -1,4 +1,6 @@
-// Copyright (C) 2009  Laboratoire de recherche et développement de l'Epita.
+// -*- coding: utf-8 -*-
+// Copyright (C) 2009, 2014 Laboratoire de recherche et développement
+// de l'Epita.
 //
 // This file is part of Spot, a model checking library.
 //
@@ -37,7 +39,7 @@ namespace spot
 	res.insert(i->second);
 	res.insert(future_conds_[dest].begin(), future_conds_[dest].end());
       }
-    future_conds_[src] = res;
+    std::swap(future_conds_[src], res);
   }
 
   future_conditions_collector::future_conditions_collector(const tgba* aut,