diff --git a/ChangeLog b/ChangeLog
index c9962f1e1..b3d1eb02e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2012-03-09  Alexandre Duret-Lutz  <adl@lrde.epita.fr>
+
+	Fix a segfault in the CGI script, reported by Denis.
+
+	* src/tgbaalgos/emptiness.cc
+	(emptiness_check_instantiator::construct): Set *err = 0
+	on success.  This avoids problem with the python bindings
+	always converting *err to a string and sometimes failing
+	to do so when err was not initialized.
+
 2012-03-08  Alexandre Duret-Lutz  <adl@lrde.epita.fr>
 
 	ltl2tgba.html: Fix initialization of unset options on reload.
diff --git a/src/tgbaalgos/emptiness.cc b/src/tgbaalgos/emptiness.cc
index b302e91ad..008526d4c 100644
--- a/src/tgbaalgos/emptiness.cc
+++ b/src/tgbaalgos/emptiness.cc
@@ -1,5 +1,5 @@
-// Copyright (C) 2009, 2011 Laboratoire de Recherche et Développement
-// de l'Epita (LRDE).
+// Copyright (C) 2009, 2011, 2012 Laboratoire de Recherche et
+// Développement de l'Epita (LRDE).
 // Copyright (C) 2004, 2005 Laboratoire d'Informatique de Paris 6 (LIP6),
 // département Systèmes Répartis Coopératifs (SRC), Université Pierre
 // et Marie Curie.
@@ -273,7 +273,10 @@ namespace spot
     ec_algo* info = ec_algos;
     for (unsigned i = 0; i < sizeof(ec_algos)/sizeof(*ec_algos); ++i, ++info)
       if (n == info->name)
-	return new emptiness_check_instantiator(o, info);
+	{
+	  *err = 0;
+	  return new emptiness_check_instantiator(o, info);
+	}
     *err = name;
     return 0;
   }