diff --git a/make-pages/Info.hs b/make-pages/Info.hs
index dfd5136..8f8a018 100644
--- a/make-pages/Info.hs
+++ b/make-pages/Info.hs
@@ -251,7 +251,8 @@ checkKeys mapping wanted = do
   keys <- getKeys mapping
   let unused = Set.toList $ keys \\ wanted
   unless (null unused) do
-    fail $ "unused keys: " <> show unused
+    fail $ "unused keys: " <> show unused <> "\n" <>
+           "expected: " <> show wanted
 
 
 instance FromYAML Info where