diff --git a/src/Data/Vec/DataFamily/SpineStrict/Optics.hs b/src/Data/Vec/DataFamily/SpineStrict/Optics.hs
--- a/src/Data/Vec/DataFamily/SpineStrict/Optics.hs
+++ b/src/Data/Vec/DataFamily/SpineStrict/Optics.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP                   #-}
 {-# LANGUAGE DataKinds             #-}
 {-# LANGUAGE FlexibleInstances     #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
@@ -32,6 +33,9 @@
 -- >>> :set -XScopedTypeVariables
 -- >>> import Prelude (Maybe (..), Char, Bool (..))
 -- >>> import Optics.Core (over, view, set, (%), review, preview)
+-- >>> import Data.Fin (Fin (..))
+-- >>> import qualified Data.Type.Nat as N
+-- >>> import Data.Vec.DataFamily.SpineStrict
 
 type LensLikeVL f s t a b = (a -> f b) -> s -> f t
 type LensLikeVL' f s a = LensLikeVL f s s a a
@@ -74,7 +78,7 @@
 {-# INLINE tailVL #-}
 
 -- | An 'I.Iso' from 'toPull' and 'fromPull'.
-_Pull :: N.InlineInduction n => L.Iso (Vec n a) (Vec n b) (P.Vec n a) (P.Vec n b)
+_Pull :: N.SNatI n => L.Iso (Vec n a) (Vec n b) (P.Vec n a) (P.Vec n b)
 _Pull = L.iso toPull fromPull
 
 -- | Prism from list.
@@ -88,7 +92,7 @@
 -- >>> review _Vec (True ::: False ::: VNil)
 -- [True,False]
 --
-_Vec :: N.InlineInduction n => L.Prism' [a] (Vec n a)
+_Vec :: N.SNatI n => L.Prism' [a] (Vec n a)
 _Vec = L.prism' toList fromList
 
 -- | Index lens.
@@ -99,12 +103,12 @@
 -- >>> set (ix (FS FZ)) 'x' ('a' ::: 'b' ::: 'c' ::: VNil)
 -- 'a' ::: 'x' ::: 'c' ::: VNil
 --
-ix :: forall n a. N.InlineInduction n => Fin n -> L.Lens' (Vec n a) a
+ix :: forall n a. N.SNatI n => Fin n -> L.Lens' (Vec n a) a
 ix i = L.lensVL (ixVL i)
 {-# INLINE ix #-}
 
-ixVL :: forall n f a. (N.InlineInduction n, Functor f) => Fin n -> LensLikeVL' f (Vec n a) a
-ixVL = getIxLens $ N.inlineInduction1 start step where
+ixVL :: forall n f a. (N.SNatI n, Functor f) => Fin n -> LensLikeVL' f (Vec n a) a
+ixVL = getIxLens $ N.induction1 start step where
     start :: IxLens f 'Z a
     start = IxLens F.absurd
 
@@ -120,24 +124,26 @@
 -- Instances
 -------------------------------------------------------------------------------
 
-instance N.InlineInduction n => L.FunctorWithIndex (Fin n) (Vec n) where
+#if !MIN_VERSION_optics_core(0,4,0)
+instance N.SNatI n => L.FunctorWithIndex (Fin n) (Vec n) where
     imap = imap
 
-instance N.InlineInduction n => L.FoldableWithIndex (Fin n) (Vec n) where
+instance N.SNatI n => L.FoldableWithIndex (Fin n) (Vec n) where
     ifoldMap = ifoldMap
     ifoldr   = ifoldr
 
-instance N.InlineInduction n => L.TraversableWithIndex (Fin n) (Vec n) where
+instance N.SNatI n => L.TraversableWithIndex (Fin n) (Vec n) where
     itraverse = itraverse
+#endif
 
-instance N.InlineInduction n => L.Each (Fin n) (Vec n a) (Vec n b) a b where
+instance N.SNatI n => L.Each (Fin n) (Vec n a) (Vec n b) a b where
 
 type instance L.Index (Vec n a)   = Fin n
 type instance L.IxValue (Vec n a) = a
 
 -- | 'Vec' doesn't have 'L.At' instance, as we __cannot__ remove value from 'Vec'.
 -- See 'ix' in "Data.Vec.DataFamily.SpineStrict" module for an 'L.Lens' (not 'L.Traversal').
-instance N.InlineInduction n => L.Ixed (Vec n a) where
+instance N.SNatI n => L.Ixed (Vec n a) where
     type IxKind (Vec n a) = L.A_Lens
     ix = ix
 
diff --git a/src/Data/Vec/Lazy/Inline/Optics.hs b/src/Data/Vec/Lazy/Inline/Optics.hs
--- a/src/Data/Vec/Lazy/Inline/Optics.hs
+++ b/src/Data/Vec/Lazy/Inline/Optics.hs
@@ -28,8 +28,11 @@
 
 -- $setup
 -- >>> :set -XScopedTypeVariables
+-- >>> import Data.Fin (Fin (..))
+-- >>> import Data.Vec.Lazy.Inline
 -- >>> import Prelude (Maybe (..), Char, Bool (..))
 -- >>> import Optics.Core (over, view, set, (%), review, preview)
+-- >>> import qualified Data.Type.Nat as N
 
 type LensLikeVL f s t a b = (a -> f b) -> s -> f t
 type LensLikeVL' f s a = LensLikeVL f s s a a
@@ -46,12 +49,12 @@
 -- >>> set (ix (FS FZ)) 'x' ('a' ::: 'b' ::: 'c' ::: VNil)
 -- 'a' ::: 'x' ::: 'c' ::: VNil
 --
-ix :: forall n a. N.InlineInduction n => Fin n -> L.Lens' (Vec n a) a
+ix :: forall n a. N.SNatI n => Fin n -> L.Lens' (Vec n a) a
 ix i = L.lensVL (ixVL i)
 {-# INLINE ix #-}
 
-ixVL :: forall n f a. (N.InlineInduction n, Functor f) => Fin n -> LensLikeVL' f (Vec n a) a
-ixVL = getIxLens $ N.inlineInduction1 start step where
+ixVL :: forall n f a. (N.SNatI n, Functor f) => Fin n -> LensLikeVL' f (Vec n a) a
+ixVL = getIxLens $ N.induction1 start step where
     start :: IxLens f 'Z a
     start = IxLens F.absurd
 
@@ -76,7 +79,7 @@
 -------------------------------------------------------------------------------
 
 -- | An 'L.Iso' from 'toPull' and 'fromPull'.
-_Pull :: N.InlineInduction n => L.Iso (Vec n a) (Vec n b) (P.Vec n a) (P.Vec n b)
+_Pull :: N.SNatI n => L.Iso (Vec n a) (Vec n b) (P.Vec n a) (P.Vec n b)
 _Pull = L.iso toPull fromPull
 
 -- | Prism from list.
@@ -90,5 +93,5 @@
 -- >>> review _Vec (True ::: False ::: VNil)
 -- [True,False]
 --
-_Vec :: N.InlineInduction n => L.Prism' [a] (Vec n a)
+_Vec :: N.SNatI n => L.Prism' [a] (Vec n a)
 _Vec = L.prism' toList fromList
diff --git a/src/Data/Vec/Lazy/Optics.hs b/src/Data/Vec/Lazy/Optics.hs
--- a/src/Data/Vec/Lazy/Optics.hs
+++ b/src/Data/Vec/Lazy/Optics.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP                   #-}
 {-# LANGUAGE DataKinds             #-}
 {-# LANGUAGE FlexibleInstances     #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
@@ -29,8 +30,11 @@
 
 -- $setup
 -- >>> :set -XScopedTypeVariables
+-- >>> import Data.Fin (Fin (..))
+-- >>> import Data.Vec.Lazy
 -- >>> import Prelude (Maybe (..), Char, Bool (..))
 -- >>> import Optics.Core (over, view, set, (%), review, preview)
+-- >>> import qualified Data.Type.Nat as N
 
 type LensLikeVL f s t a b = (a -> f b) -> s -> f t
 type LensLikeVL' f s a = LensLikeVL f s s a a
@@ -114,6 +118,7 @@
 -- Instances
 -------------------------------------------------------------------------------
 
+#if !MIN_VERSION_optics_core(0,4,0)
 instance L.FunctorWithIndex (Fin n) (Vec n) where
     imap = imap
 
@@ -123,6 +128,7 @@
 
 instance L.TraversableWithIndex (Fin n) (Vec n) where
     itraverse = itraverse
+#endif
 
 instance L.Each (Fin n) (Vec n a) (Vec n b) a b where
 
diff --git a/src/Data/Vec/Pull/Optics.hs b/src/Data/Vec/Pull/Optics.hs
--- a/src/Data/Vec/Pull/Optics.hs
+++ b/src/Data/Vec/Pull/Optics.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP                   #-}
 {-# LANGUAGE DataKinds             #-}
 {-# LANGUAGE GADTs                 #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
@@ -24,6 +25,8 @@
 
 -- $setup
 -- >>> :set -XScopedTypeVariables
+-- >>> import Data.Fin (Fin (..))
+-- >>> import Data.Vec.Pull
 -- >>> import Optics.Core (over, view, set, (%))
 -- >>> import qualified Data.Vec.Lazy as L
 -- >>> import qualified Data.Vec.Lazy.Optics as L
@@ -102,9 +105,11 @@
 -- Instances
 -------------------------------------------------------------------------------
 
+#if !MIN_VERSION_optics_core(0,4,0)
 instance L.FunctorWithIndex (Fin n) (Vec n) where
     imap = imap
 
 instance N.SNatI n => L.FoldableWithIndex (Fin n) (Vec n) where
     ifoldMap = ifoldMap
     ifoldr   = ifoldr
+#endif
diff --git a/vec-optics.cabal b/vec-optics.cabal
--- a/vec-optics.cabal
+++ b/vec-optics.cabal
@@ -1,6 +1,6 @@
 cabal-version:      2.2
 name:               vec-optics
-version:            0.3
+version:            0.4
 synopsis:           Vec: length-indexed (sized) list: optics support
 category:           Data, Dependent Types, Optics
 description:
@@ -16,10 +16,17 @@
 license-file:       LICENSE
 author:             Oleg Grenrus <oleg.grenrus@iki.fi>
 maintainer:         Oleg.Grenrus <oleg.grenrus@iki.fi>
-copyright:          (c) 2017-2019 Oleg Grenrus
+copyright:          (c) 2017-2021 Oleg Grenrus
 build-type:         Simple
 extra-source-files: ChangeLog.md
-tested-with:        GHC ==8.0.2 || ==8.2.2 || ==8.4.4 || ==8.6.5 || ==8.8.1
+tested-with:
+  GHC ==8.0.2
+   || ==8.2.2
+   || ==8.4.4
+   || ==8.6.5
+   || ==8.8.4
+   || ==8.10.4
+   || ==9.0.1
 
 source-repository head
   type:     git
@@ -38,15 +45,15 @@
     Data.Vec.Pull.Optics
 
   -- GHC boot libs
-  build-depends:    base >=4.9 && <4.14
+  build-depends:    base >=4.9 && <4.16
 
   -- siblings
   build-depends:
-    , fin  ^>=0.1.1
-    , vec  ^>=0.3
+    , fin  ^>=0.2
+    , vec  ^>=0.4
 
   -- other dependencies
-  build-depends:    optics-core ^>=0.2
+  build-depends:    optics-core >=0.2 && <0.5
   other-extensions:
     CPP
     FlexibleContexts