diff --git a/harness/Darcs/Test/Patch.hs b/harness/Darcs/Test/Patch.hs
index f50f6b9..f0f4e2a 100644
--- a/harness/Darcs/Test/Patch.hs
+++ b/harness/Darcs/Test/Patch.hs
@@ -244,3 +244,3 @@ properties :: forall thing gen. (Show1 gen, Arbitrary (Sealed gen)) =>
 properties gen prefix genname tests =
-  [ cond name condition check | (name, condition, check) <- tests ]
+  [ cond name condition check | (name, condition :: TestCondition thing, check :: TestCheck thing testable) <- tests ]
   where cond :: forall testable. Testable testable