diff --git a/ChangeLog b/ChangeLog
index 16a66fb85..c9cf8b4b4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2011-02-09  Alexandre Duret-Lutz  <adl@lrde.epita.fr>
+
+	Avoid running "dot" when it is not installed...
+
+	* src/tgbatest/kv.test: Do not run dot if it is not installed.
+	* iface/nips/nipstest/dotty.test: Likewise
+
 2011-02-08  Alexandre Duret-Lutz  <adl@lrde.epita.fr>
 
 	Add some tricks into HACKING.
diff --git a/iface/nips/nipstest/dotty.test b/iface/nips/nipstest/dotty.test
index a42cabcde..7573dfbb1 100755
--- a/iface/nips/nipstest/dotty.test
+++ b/iface/nips/nipstest/dotty.test
@@ -1,5 +1,5 @@
 #!/bin/sh
-# Copyright (C) 2008 Laboratoire de Recherche et Développement de
+# Copyright (C) 2008, 2011 Laboratoire de Recherche et Développement de
 # l'Epita (LRDE)
 #
 # This file is part of Spot, a model checking library.
@@ -26,6 +26,6 @@ set -e
 BYTECODE="never.pr.b regbit.b"
 for bytecode in $BYTECODE; do
     run 0 "$top_builddir/dottynips" "$srcdir/$bytecode" > dotty || exit 1
-    "$DOT" -Tps dotty > /dev/null || exit 1
+    "${DOT-:}" -Tps dotty > /dev/null || exit 1
     rm -f dotty
 done
diff --git a/src/tgbatest/kv.test b/src/tgbatest/kv.test
index 45dab503a..b3495b46d 100755
--- a/src/tgbatest/kv.test
+++ b/src/tgbatest/kv.test
@@ -1,5 +1,6 @@
 #!/bin/sh
-# Copyright (C) 2009, 2010  Laboratoire de Recherche et Development de l'EPITA.
+# Copyright (C) 2009, 2010, 2011 Laboratoire de Recherche et
+# Development de l'EPITA.
 #
 # This file is part of Spot, a model checking library.
 #
@@ -26,7 +27,7 @@ set -e
 check ()
 {
   run 0 ../ltl2tgba -f -KV "$1" > out.dot
-  $DOT out.dot > /dev/null
+  "${DOT-:}" out.dot > /dev/null
   rm -f out.dot
 }