diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,10 @@
 # Version history for ral
 
+## 0.2
+
+- Support `fin-0.2`
+- Support `lens-5`
+
 ## 0.1
 
 - First version. Released on an unsuspecting world.
diff --git a/ral-lens.cabal b/ral-lens.cabal
--- a/ral-lens.cabal
+++ b/ral-lens.cabal
@@ -1,6 +1,6 @@
 cabal-version:      2.2
 name:               ral-lens
-version:            0.1
+version:            0.2
 synopsis:           Length-indexed random access lists: lens utilities.
 category:           Data, Dependent Types, Singletons, Lens
 description:
@@ -13,7 +13,7 @@
 license-file:       LICENSE
 author:             Oleg Grenrus <oleg.grenrus@iki.fi>
 maintainer:         Oleg.Grenrus <oleg.grenrus@iki.fi>
-copyright:          (c) 2019 Oleg Grenrus
+copyright:          (c) 2019-2021 Oleg Grenrus
 build-type:         Simple
 extra-source-files: ChangeLog.md
 tested-with:
@@ -23,7 +23,9 @@
    || ==8.2.2
    || ==8.4.4
    || ==8.6.5
-   || ==8.8.1
+   || ==8.8.4
+   || ==8.10.4
+   || ==9.0.1
 
 source-repository head
   type:     git
@@ -39,14 +41,15 @@
     Data.RAList.NonEmpty.Lens
     Data.RAVec.Lens
     Data.RAVec.NonEmpty.Lens
+    Data.RAVec.Tree.DF.Lens
     Data.RAVec.Tree.Lens
 
   build-depends:
-    , base  >=4.7   && <4.14
+    , base  >=4.7   && <4.16
     , bin   ^>=0.1
-    , fin   ^>=0.1.1
-    , lens  >=4.16  && <4.19
-    , ral   ^>=0.1
+    , fin   ^>=0.2
+    , lens  >=4.16  && <5.1
+    , ral   ^>=0.2
 
 -- dump-core
 -- if impl(ghc >= 8.0)
diff --git a/src/Data/RAList/Lens.hs b/src/Data/RAList/Lens.hs
--- a/src/Data/RAList/Lens.hs
+++ b/src/Data/RAList/Lens.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP                   #-}
 {-# LANGUAGE FlexibleInstances     #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE RankNTypes            #-}
@@ -28,6 +29,7 @@
 -- Instances
 -------------------------------------------------------------------------------
 
+#if !MIN_VERSION_lens(5,0,0)
 instance L.FunctorWithIndex Int RAList where
     imap = imap
 
@@ -36,6 +38,7 @@
 
 instance L.TraversableWithIndex Int RAList where
     itraverse = itraverse
+#endif
 
 instance L.Each (RAList a) (RAList b) a b
 
@@ -43,4 +46,4 @@
 type instance L.IxValue (RAList a) = a
 
 instance L.Ixed (RAList a) where
-    ix = ix
+    ix i = ix i
diff --git a/src/Data/RAList/NonEmpty/Lens.hs b/src/Data/RAList/NonEmpty/Lens.hs
--- a/src/Data/RAList/NonEmpty/Lens.hs
+++ b/src/Data/RAList/NonEmpty/Lens.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP                   #-}
 {-# LANGUAGE FlexibleInstances     #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE RankNTypes            #-}
@@ -49,6 +50,7 @@
 -- Instances
 -------------------------------------------------------------------------------
 
+#if !MIN_VERSION_lens(5,0,0)
 instance L.FunctorWithIndex Int NERAList where
     imap = imap
 
@@ -57,6 +59,7 @@
 
 instance L.TraversableWithIndex Int NERAList where
     itraverse = itraverse
+#endif
 
 instance L.Each (NERAList a) (NERAList b) a b
 
@@ -64,4 +67,4 @@
 type instance L.IxValue (NERAList a) = a
 
 instance L.Ixed (NERAList a) where
-    ix = ix
+    ix i = ix i
diff --git a/src/Data/RAVec/Lens.hs b/src/Data/RAVec/Lens.hs
--- a/src/Data/RAVec/Lens.hs
+++ b/src/Data/RAVec/Lens.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP                   #-}
 {-# LANGUAGE FlexibleInstances     #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE RankNTypes            #-}
@@ -20,6 +21,7 @@
 -- $setup
 -- >>> import Control.Lens ((^.), (&), (.~), (^?), (#))
 -- >>> import Prelude
+-- >>> import Data.RAVec
 -- >>> import qualified Data.Type.Bin as B
 
 -------------------------------------------------------------------------------
@@ -38,6 +40,7 @@
 -- Instances
 -------------------------------------------------------------------------------
 
+#if !MIN_VERSION_lens(5,0,0)
 instance L.FunctorWithIndex (Pos b) (RAVec b) where
     imap = imap
 
@@ -47,6 +50,7 @@
 
 instance L.TraversableWithIndex (Pos b) (RAVec b) where
     itraverse = itraverse
+#endif
 
 instance L.Each (RAVec n a) (RAVec n b) a b where
     each = traverse
@@ -55,4 +59,4 @@
 type instance L.IxValue (RAVec n a) = a
 
 instance L.Ixed (RAVec b a) where
-    ix = ix
+    ix i = ix i
diff --git a/src/Data/RAVec/NonEmpty/Lens.hs b/src/Data/RAVec/NonEmpty/Lens.hs
--- a/src/Data/RAVec/NonEmpty/Lens.hs
+++ b/src/Data/RAVec/NonEmpty/Lens.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP                   #-}
 {-# LANGUAGE FlexibleInstances     #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE RankNTypes            #-}
@@ -39,6 +40,7 @@
 -- Instances
 -------------------------------------------------------------------------------
 
+#if !MIN_VERSION_lens(5,0,0)
 instance L.FunctorWithIndex (PosP b) (NERAVec b) where
     imap = imap
 
@@ -58,6 +60,7 @@
 
 instance L.TraversableWithIndex (PosP' n b) (NERAVec' n b) where
     itraverse = itraverse'
+#endif
 
 instance L.Each (NERAVec n a) (NERAVec n b) a b where
     each = traverse
@@ -72,7 +75,7 @@
 type instance L.IxValue (NERAVec' n b a) = a
 
 instance L.Ixed (NERAVec b a) where
-    ix = ix
+    ix i = ix i
 
 instance L.Ixed (NERAVec' n b a) where
-    ix = ix'
+    ix i = ix' i
diff --git a/src/Data/RAVec/Tree/DF/Lens.hs b/src/Data/RAVec/Tree/DF/Lens.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/RAVec/Tree/DF/Lens.hs
@@ -0,0 +1,65 @@
+{-# LANGUAGE CPP                   #-}
+{-# LANGUAGE FlexibleInstances     #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE RankNTypes            #-}
+{-# LANGUAGE TypeFamilies          #-}
+{-# OPTIONS_GHC -fno-warn-orphans #-}
+module Data.RAVec.Tree.DF.Lens (
+    -- * Indexing
+    ix,
+    ) where
+
+import Control.Applicative ((<$>))
+import Data.Wrd            (Wrd (..))
+import Prelude ()
+
+import qualified Control.Lens  as L
+import qualified Data.Type.Nat as N
+
+import Data.RAVec.Tree.DF
+
+-- $setup
+-- >>> import Control.Lens ((^.), (&), (.~), (^?), (#))
+-- >>> import Prelude
+-- >>> import Data.RAVec.Tree.DF
+-- >>> import Data.Wrd (Wrd (..))
+
+-------------------------------------------------------------------------------
+-- Indexing
+-------------------------------------------------------------------------------
+
+-- | Index lens.
+--
+-- >>> let tree = Node (Node (Leaf 'a') (Leaf 'b')) (Node (Leaf 'c') (Leaf 'd'))
+-- >>> tree & ix (W1 $ W0 WE) .~ 'z'
+-- Node (Node (Leaf 'a') (Leaf 'b')) (Node (Leaf 'z') (Leaf 'd'))
+--
+ix :: Wrd n -> L.Lens' (Tree n a) a
+ix WE      f (Leaf x)   = Leaf <$> f x
+ix (W0 is) f (Node x y) = (`Node` y) <$> ix is f x
+ix (W1 is) f (Node x y) = (x `Node`) <$> ix is f y
+
+-------------------------------------------------------------------------------
+-- Instances
+-------------------------------------------------------------------------------
+
+#if !MIN_VERSION_lens(5,0,0)
+instance N.SNatI n => L.FunctorWithIndex (Wrd n) (Tree n) where
+    imap = imap
+
+instance N.SNatI n => L.FoldableWithIndex (Wrd n) (Tree n) where
+    ifoldMap = ifoldMap
+    ifoldr   = ifoldr
+    ifoldl   = ifoldl
+
+instance N.SNatI n => L.TraversableWithIndex (Wrd n) (Tree n) where
+    itraverse = itraverse
+#endif
+
+instance N.SNatI n => L.Each (Tree n a) (Tree n b) a b
+
+type instance L.Index (Tree n a)   = Wrd n
+type instance L.IxValue (Tree n a) = a
+
+instance L.Ixed (Tree n a) where
+    ix i = ix i
diff --git a/src/Data/RAVec/Tree/Lens.hs b/src/Data/RAVec/Tree/Lens.hs
--- a/src/Data/RAVec/Tree/Lens.hs
+++ b/src/Data/RAVec/Tree/Lens.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP                   #-}
 {-# LANGUAGE FlexibleInstances     #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE RankNTypes            #-}
@@ -18,6 +19,8 @@
 
 -- $setup
 -- >>> import Control.Lens ((^.), (&), (.~), (^?), (#))
+-- >>> import Data.RAVec.Tree
+-- >>> import Data.Wrd (Wrd (..))
 -- >>> import Prelude
 
 -------------------------------------------------------------------------------
@@ -39,6 +42,7 @@
 -- Instances
 -------------------------------------------------------------------------------
 
+#if !MIN_VERSION_lens(5,0,0)
 instance L.FunctorWithIndex (Wrd n) (Tree n) where
     imap = imap
 
@@ -49,6 +53,7 @@
 
 instance L.TraversableWithIndex (Wrd n) (Tree n) where
     itraverse = itraverse
+#endif
 
 instance L.Each (Tree n a) (Tree n b) a b
 
@@ -56,4 +61,4 @@
 type instance L.IxValue (Tree n a) = a
 
 instance L.Ixed (Tree n a) where
-    ix = ix
+    ix i = ix i