diff --git a/PersistEvaluationScheme.hs b/PersistEvaluationScheme.hs
index 28ee1d1..14d11b7 100644
--- a/PersistEvaluationScheme.hs
+++ b/PersistEvaluationScheme.hs
@@ -11,7 +11,7 @@ instance PersistField EvaluationScheme where
 
   fromPersistValue (PersistText t) = case readMay t of
     Just val -> Right val
-    Nothing -> Left "Unexpected value"
+    Nothing -> Left $ "Unexpected value '" ++ t ++ "'"
   fromPersistValue _ = Left "Unexpected value"
 
 instance PersistFieldSql EvaluationScheme where