diff --git a/isomorphism-class.cabal b/isomorphism-class.cabal
--- a/isomorphism-class.cabal
+++ b/isomorphism-class.cabal
@@ -1,6 +1,6 @@
 cabal-version: 3.0
 name: isomorphism-class
-version: 0.2.0.3
+version: 0.2.1
 synopsis: Lawful typeclasses for conversion between types
 category: Conversion
 homepage: https://github.com/nikita-volkov/isomorphism-class
@@ -65,7 +65,7 @@
     IsomorphismClass.Relations.Int8AndWord8
     IsomorphismClass.Relations.IntAndWord
     IsomorphismClass.Relations.IntMapAndMapOfInt
-    IsomorphismClass.Relations.IntSetAndSetOfInts
+    IsomorphismClass.Relations.IntSetAndSetOfInt
     IsomorphismClass.Relations.LazyByteStringAndLazyByteStringBuilder
     IsomorphismClass.Relations.LazyByteStringAndLazyText
     IsomorphismClass.Relations.LazyByteStringAndShortByteString
diff --git a/library/IsomorphismClass/Classes/IsSome.hs b/library/IsomorphismClass/Classes/IsSome.hs
--- a/library/IsomorphismClass/Classes/IsSome.hs
+++ b/library/IsomorphismClass/Classes/IsSome.hs
@@ -23,6 +23,8 @@
 --
 -- > \a -> maybeFrom (to a) == Just a
 --
+-- === Testing
+--
 -- For testing whether your instances conform to these laws use 'IsomorphismClass.isSomeLawsProperties'.
 class IsSome sup sub where
   -- |
diff --git a/library/IsomorphismClass/Proxies/ViaIsSome.hs b/library/IsomorphismClass/Proxies/ViaIsSome.hs
--- a/library/IsomorphismClass/Proxies/ViaIsSome.hs
+++ b/library/IsomorphismClass/Proxies/ViaIsSome.hs
@@ -1,6 +1,6 @@
 module IsomorphismClass.Proxies.ViaIsSome where
 
-import IsomorphismClass.Classes.IsSome
+import IsomorphismClass.Classes
 import IsomorphismClass.Prelude
 import qualified Test.QuickCheck as QuickCheck
 
@@ -11,7 +11,7 @@
 --
 -- > newtype Percent = Percent Double
 -- >   deriving newtype (Show, Eq, Ord)
--- >   deriving (Read, IsString, Arbitrary) via (ViaIsSome Double Percent)
+-- >   deriving (Read, Arbitrary) via (ViaIsSome Double Percent)
 -- >
 -- > instance IsSome Double Percent where
 -- >   to (Percent double) = double
@@ -27,6 +27,16 @@
 instance (IsSome sup sub) => IsSome sup (ViaIsSome sup sub) where
   to (ViaIsSome a) = to a
   maybeFrom = fmap ViaIsSome . maybeFrom
+
+instance IsSome sub (ViaIsSome sup sub) where
+  to = coerce
+
+instance IsSome (ViaIsSome sup sub) sub where
+  to = coerce
+
+instance Is sub (ViaIsSome sup sub)
+
+instance Is (ViaIsSome sup sub) sub
 
 instance (IsSome sup sub, Show sup) => Show (ViaIsSome sup sub) where
   show (ViaIsSome a) = show (to @sup a)
diff --git a/library/IsomorphismClass/Relations/IntSetAndSetOfInt.hs b/library/IsomorphismClass/Relations/IntSetAndSetOfInt.hs
new file mode 100644
--- /dev/null
+++ b/library/IsomorphismClass/Relations/IntSetAndSetOfInt.hs
@@ -0,0 +1,16 @@
+{-# OPTIONS_GHC -Wno-orphans #-}
+
+module IsomorphismClass.Relations.IntSetAndSetOfInt where
+
+import IsomorphismClass.Classes
+import IsomorphismClass.Prelude
+
+instance IsSome (Set Int) IntSet where
+  to = fromList . toList
+
+instance IsSome IntSet (Set Int) where
+  to = fromList . toList
+
+instance Is (Set Int) IntSet
+
+instance Is IntSet (Set Int)
diff --git a/library/IsomorphismClass/Relations/IntSetAndSetOfInts.hs b/library/IsomorphismClass/Relations/IntSetAndSetOfInts.hs
deleted file mode 100644
--- a/library/IsomorphismClass/Relations/IntSetAndSetOfInts.hs
+++ /dev/null
@@ -1,16 +0,0 @@
-{-# OPTIONS_GHC -Wno-orphans #-}
-
-module IsomorphismClass.Relations.IntSetAndSetOfInts where
-
-import IsomorphismClass.Classes
-import IsomorphismClass.Prelude
-
-instance IsSome (Set Int) IntSet where
-  to = fromList . toList
-
-instance IsSome IntSet (Set Int) where
-  to = fromList . toList
-
-instance Is (Set Int) IntSet
-
-instance Is IntSet (Set Int)