diff --git a/lawful-conversions.cabal b/lawful-conversions.cabal
--- a/lawful-conversions.cabal
+++ b/lawful-conversions.cabal
@@ -1,6 +1,6 @@
 cabal-version: 3.0
 name: lawful-conversions
-version: 0.2
+version: 0.2.0.1
 synopsis: Lawful typeclasses for bidirectional conversion between types
 category: Conversion
 homepage: https://github.com/nikita-volkov/lawful-conversions
diff --git a/src/library/LawfulConversions/Properties.hs b/src/library/LawfulConversions/Properties.hs
--- a/src/library/LawfulConversions/Properties.hs
+++ b/src/library/LawfulConversions/Properties.hs
@@ -54,6 +54,7 @@
 -- >       (uncurry prop)
 -- >       (isManyProperties @String @Text Proxy Proxy)
 isManyProperties ::
+  forall a b.
   (IsMany a b, Eq a, Eq b, Show a, Show b, Arbitrary a, Arbitrary b) =>
   Proxy a ->
   Proxy b ->
@@ -63,9 +64,9 @@
       property \b -> b === from' (to' b)
     ),
     ( "'from' is consistent with 'maybeFrom'",
-      property \a -> case maybeFrom a of
-        Nothing -> property Discard
-        Just b -> b === from' a
+      property \(b :: b) ->
+        let a = to @a b
+         in maybeFrom (to @a b) === Just (from @a @b a)
     ),
     ( "'to' after 'from' always succeeds with 'maybeFrom'",
       property \a ->