diff --git a/src/tgbaalgos/simulation.cc b/src/tgbaalgos/simulation.cc
index 0a58565f0..a2094276b 100644
--- a/src/tgbaalgos/simulation.cc
+++ b/src/tgbaalgos/simulation.cc
@@ -394,7 +394,17 @@ namespace spot
             free_var_.pop();
           }
 
-	assert(bdd_lstate_.size() == used_var_.size());
+	for (int i = 0; i > nb_new_color; --i)
+          {
+            assert(!used_var_.empty());
+            free_var_.push(bdd_var(used_var_.front()));
+            used_var_.pop_front();
+          }
+
+
+	assert((bdd_lstate_.size() == used_var_.size())
+               || (bdd_lstate_.find(bddfalse) != bdd_lstate_.end()
+                   && bdd_lstate_.size() == used_var_.size() + 1));
 
 	// Now we make a temporary hash_table which links the tuple
 	// "C^(i-1), N^(i-1)" to the new class coloring.  If we
diff --git a/src/tgbatest/Makefile.am b/src/tgbatest/Makefile.am
index 70198270a..f9d95a427 100644
--- a/src/tgbatest/Makefile.am
+++ b/src/tgbatest/Makefile.am
@@ -76,6 +76,7 @@ TESTS = \
   explicit2.test \
   taatgba.test \
   tgbaread.test \
+  renault.test \
   neverclaimread.test \
   readsave.test \
   ltl2tgba.test \
diff --git a/src/tgbatest/renault.test b/src/tgbatest/renault.test
new file mode 100755
index 000000000..e413a1555
--- /dev/null
+++ b/src/tgbatest/renault.test
@@ -0,0 +1,58 @@
+#!/bin/sh
+# -*- coding: utf-8 -*-
+# Copyright (C) 2012 Laboratoire de Recherche et Développement
+# de l'Epita (LRDE).
+#
+# This file is part of Spot, a model checking library.
+#
+# Spot is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# Spot is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+# License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Spot; see the file COPYING.  If not, write to the Free
+# Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+# 02111-1307, USA.
+
+. ./defs
+set -e
+
+cat >file <<EOF
+acc = "IOP.clear_interrupts";
+"1", "2", "a & b",;
+"1", "3", "(!a & !b & !c) | (c & a)",;
+"1", "1", "(!a & !b & !c) | (c & a)", "IOP.clear_interrupts";
+"1", "4", "!a & !c",;
+"1", "5", "!a & !c", "IOP.clear_interrupts";
+"1", "6", "a & b",;
+"2", "2", "a & b",;
+"2", "3", "c & a",;
+"2", "1", "c & a", "IOP.clear_interrupts";
+"2", "6", "a & b",;
+"3", "8", "1",;
+"4", "10", "!c",;
+"4", "8", "!b & !c",;
+"5", "3", "!a & !b & !c",;
+"5", "1", "!a & !b & !c", "IOP.clear_interrupts";
+"5", "4", "!a & !c",;
+"5", "5", "!a & !c", "IOP.clear_interrupts";
+"6", "7", "b",;
+"6", "8", "c",;
+"7", "9", "b & !c & !d",;
+"9", "9", "b & !c",;
+EOF
+
+cat >outexp <<EOF
+transitions: 12
+states: 6
+EOF
+
+run 0 ../ltl2tgba -X -ks -RDS file > out
+
+cmp out outexp