diff --git a/x/lib/clutter.xml b/x/lib/clutter.xml
index ad635ef74e..858aedea85 100644
--- a/x/lib/clutter.xml
+++ b/x/lib/clutter.xml
@@ -136,8 +136,9 @@ autoreconf -f -i</userinput></screen>
 make</userinput></screen>
 
     <para>
-      To test the results, issue: <command>make -k check</command> (you must be
+      To test the results, issue: <command>make -j1 -k check</command> (you must be
       in an xterm or similar to do this, because it launches some windows).
+      <!-- The tests will hang if run at more than -j1.-->
       <!-- The test named actor-offscreen-redirect may hang.-->
       <!-- Two tests have been observed to indicate ERROR, but each is flagged twice. 
            For version 1.26.4 all tests pass.  -->