--- a/Quot/quotient_tacs.ML	Mon Feb 08 11:41:25 2010 +0100
+++ b/Quot/quotient_tacs.ML	Mon Feb 08 11:56:22 2010 +0100
@@ -654,10 +654,9 @@
   val ctxt = Context.proof_of context
   val ((_, [thm']), ctxt') = Variable.import false [thm] ctxt
   val goal = (quotient_lift_all ctxt' o prop_of) thm'
-  val nthm = Goal.prove ctxt' [] [] goal (fn x => lift_tac ctxt' [thm] 1)
-  val [nthm1] = ProofContext.export ctxt' ctxt [nthm]
 in
-  nthm1
+  Goal.prove ctxt' [] [] goal (K (lift_tac ctxt' [thm] 1))
+  |> singleton (ProofContext.export ctxt' ctxt)
 end;
 
 val lifted_attrib = Thm.rule_attribute lifted_attrib_aux