diff --git a/Changelog.md b/Changelog.md
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,5 +1,11 @@
 # NEXT
 
+# 0.4.1
+
+* Add `MonadFail` instances for `LFreshMT` and `FreshMT`
+
+* Builds with GHC 8.10
+
 # 0.4.0
 
 * New binding specification type `Ignore`.
diff --git a/examples/Prof.hs b/examples/Prof.hs
deleted file mode 100644
--- a/examples/Prof.hs
+++ /dev/null
@@ -1,42 +0,0 @@
-{-# language GADTs, RankNTypes #-}
-module Prof where
-
-import Data.Profunctor
-
-data Shop a b s t where
-  Shop :: (s -> a) -> (s -> b -> t) -> Shop a b s t
-
-type Optic p s t a b  = p a b -> p s t
-type Lens s t a b = forall p . (Strong p) => Optic p s t a b
-
-lens :: (s -> a) -> (s -> b -> t) -> Lens s t a b
-lens get set pab = dimap (\s -> (s, get s)) (uncurry set) (second' pab)
-
-instance Profunctor (Shop a b) where
-  dimap f g (Shop get set) = Shop (get . f) (\s -> g . set (f s))
-
-instance Strong (Shop a b) where
-   first' (Shop get set) = Shop (get . fst) (\(s,c) b -> (set s b, c))
-
-withLens :: Lens s t a b -> ((s -> a) -> (s -> b -> t) -> r) -> r
-withLens l k = case l (Shop id (const id)) of
-                 Shop getter setter -> k getter setter
-
-
-type Prism s t a b = forall p . (Choice p) => Optic p s t a b
-
-prism :: (s -> Either t a) -> (b -> t) -> Prism s t a b
-prism view review pab = dimap view (either id review) (right' pab)
-
-data Market a b s t where
-  Market :: (s -> Either t a) -> (b -> t) -> Market a b s t
-
-instance Profunctor (Market a b) where
-  dimap f g (Market view review) = Market (either (Left . g) Right . (view . f)) (g . review)
-
-instance Choice (Market a b) where
-  left' (Market view review) = Market (either (either (Left . Left) Right . view) (Left . Right)) (Left . review)
-
-withPrism :: Prism s t a b -> ((s -> Either t a) -> (b -> t) -> r) -> r
-withPrism l k = case l (Market Right id) of
-                  Market view review -> k view review
diff --git a/src/Unbound/Generics/LocallyNameless/Fresh.hs b/src/Unbound/Generics/LocallyNameless/Fresh.hs
--- a/src/Unbound/Generics/LocallyNameless/Fresh.hs
+++ b/src/Unbound/Generics/LocallyNameless/Fresh.hs
@@ -8,6 +8,7 @@
 -- Global freshness monad.
 {-# LANGUAGE CPP, GeneralizedNewtypeDeriving,
              FlexibleInstances, MultiParamTypeClasses,
+             StandaloneDeriving,
              UndecidableInstances
   #-}
 -- (we expect deprecation warnings about Control.Monad.Trans.Error)
@@ -20,6 +21,9 @@
 import Control.Monad.Identity
 
 import Control.Monad.Catch (MonadThrow, MonadCatch, MonadMask)
+#if MIN_VERSION_base(4,9,0)
+import qualified Control.Monad.Fail as Fail
+#endif
 import Control.Monad.Trans
 import Control.Monad.Trans.Except
 import Control.Monad.Trans.Error
@@ -66,6 +70,10 @@
     , MonadCatch
     , MonadMask
     )
+
+#if MIN_VERSION_base(4,9,0)
+deriving instance Fail.MonadFail m => Fail.MonadFail (FreshMT m)
+#endif
 
 -- | Run a 'FreshMT' computation (with the global index starting at zero).
 runFreshMT :: Monad m => FreshMT m a -> m a
diff --git a/src/Unbound/Generics/LocallyNameless/LFresh.hs b/src/Unbound/Generics/LocallyNameless/LFresh.hs
--- a/src/Unbound/Generics/LocallyNameless/LFresh.hs
+++ b/src/Unbound/Generics/LocallyNameless/LFresh.hs
@@ -45,6 +45,7 @@
              , GeneralizedNewtypeDeriving
              , FlexibleInstances
              , MultiParamTypeClasses
+             , StandaloneDeriving
              , UndecidableInstances #-}
 module Unbound.Generics.LocallyNameless.LFresh
        (
@@ -64,6 +65,9 @@
 import Data.Typeable (Typeable)
 
 import Control.Monad.Catch (MonadThrow, MonadCatch, MonadMask)
+#if MIN_VERSION_base(4,9,0)
+import qualified Control.Monad.Fail as Fail
+#endif
 import Control.Monad.Reader
 import Control.Monad.Identity
 import Control.Applicative (Applicative, Alternative)
@@ -115,6 +119,10 @@
     , MonadCatch
     , MonadMask
     )
+
+#if MIN_VERSION_base(4,9,0)
+deriving instance Fail.MonadFail m => Fail.MonadFail (LFreshMT m)
+#endif
 
 -- | Run an 'LFreshMT' computation in an empty context.
 runLFreshMT :: LFreshMT m a -> m a
diff --git a/src/Unbound/Generics/LocallyNameless/Name.hs b/src/Unbound/Generics/LocallyNameless/Name.hs
--- a/src/Unbound/Generics/LocallyNameless/Name.hs
+++ b/src/Unbound/Generics/LocallyNameless/Name.hs
@@ -35,7 +35,7 @@
 -- type @a@.  The type @a@ is used as a tag to distinguish these names
 -- from names that may stand for other sorts of terms.
 --
--- Two names in a term are consider
+-- Two names in a term are considered
 -- 'Unbound.Generics.LocallyNameless.Operations.aeq' equal when they
 -- are the same name (in the sense of '(==)').  In patterns, however,
 -- any two names are equal if they occur in the same place within the
diff --git a/test/Calc.hs b/test/Calc.hs
--- a/test/Calc.hs
+++ b/test/Calc.hs
@@ -5,9 +5,12 @@
 -- Maintainer : Aleksey Kliger
 -- Stability  : experimental
 --
-{-# LANGUAGE DeriveGeneric, DeriveDataTypeable #-}
+{-# LANGUAGE CPP, DeriveGeneric, DeriveDataTypeable #-}
 module Calc where
 
+#if MIN_VERSION_base(4,9,0) && !MIN_VERSION_base(4,13,0)
+import Control.Monad.Fail (MonadFail)
+#endif
 import Control.Arrow (second)
 import Data.Typeable (Typeable)
 import GHC.Generics (Generic)
@@ -67,7 +70,11 @@
 extendEnv v e rho w =
   if v == w then Just e else rho w
 
-whnf :: (Fresh m) => Env -> Expr -> m Expr
+whnf :: (
+#if MIN_VERSION_base(4,9,0)
+  MonadFail m,
+#endif
+  Fresh m) => Env -> Expr -> m Expr
 whnf rho (V v) = case rho v of
   Just e -> return e
   Nothing -> fail $ "unbound variable " ++ show v
@@ -76,7 +83,11 @@
   v1 <- whnf rho e1
   v2 <- whnf rho e2
   add v1 v2
-  where add :: Monad m => Expr -> Expr -> m Expr
+  where add :: (
+#if MIN_VERSION_base(4,9,0)
+          MonadFail m,
+#endif
+          Monad m) => Expr -> Expr -> m Expr
         add (C i1) (C i2) = return (C $ i1 + i2)
         add _ _ = fail "add of two non-integers"
 whnf rho0 (Let b) = do
@@ -91,7 +102,11 @@
   rho' <- whnfLsb lsb rho0
   whnf rho' body
 
-whnfLsb :: Fresh m => LetStarBinds -> Env -> m Env
+whnfLsb :: (
+#if MIN_VERSION_base(4,9,0)
+  MonadFail m,
+#endif
+  Fresh m) => LetStarBinds -> Env -> m Env
 whnfLsb EmptyLSB = return
 whnfLsb (ConsLSB rbnd) = \rho -> do
   let ((v, Embed e), lsb) = unrebind rbnd
diff --git a/unbound-generics.cabal b/unbound-generics.cabal
--- a/unbound-generics.cabal
+++ b/unbound-generics.cabal
@@ -2,7 +2,7 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                unbound-generics
-version:             0.4.0
+version:             0.4.1
 synopsis:            Support for programming with names and binders using GHC Generics
 description:         Specify the binding structure of your data type with an
                      expressive set of type combinators, and unbound-generics
@@ -22,14 +22,14 @@
 license-file:        LICENSE
 author:              Aleksey Kliger
 maintainer:          aleksey@lambdageek.org
-copyright:           (c) 2014-2018, Aleksey Kliger
+copyright:           (c) 2014-2020, Aleksey Kliger
 category:            Language
 build-type:          Simple
 extra-source-files:  examples/*.hs, examples/*.lhs,
                      README.md,
                      Changelog.md
 cabal-version:       >=1.10
-tested-with: GHC == 7.6.3, GHC == 7.8.4, GHC == 7.10.3, GHC == 8.0.*, GHC == 8.2.*, GHC == 8.4.*, GHC == 8.6.*
+tested-with: GHC == 7.8.4, GHC == 7.10.3, GHC == 8.0.2, GHC == 8.2.2, GHC == 8.4.4, GHC == 8.6.5, GHC == 8.8.3, GHC == 8.10.*
              
 library
   exposed-modules:     Unbound.Generics.LocallyNameless