--- a/ProgTutorial/FirstSteps.thy	Tue Jul 21 13:27:39 2009 +0200
+++ b/ProgTutorial/FirstSteps.thy	Tue Jul 21 13:31:23 2009 +0200
@@ -1171,7 +1171,7 @@
   the file @{ML_file "Pure/thm.ML"}.
   \end{readmore}
 
-  \begin{exercise}
+  \begin{exercise}\label{fun:revsum typed}
   Check that the function defined in Exercise~\ref{fun:revsum} returns a
   result that type-checks.
   \end{exercise}