diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog for harg
 
+## 0.4.0.0 [2019.09.16]
+
+- Fix wrong name in previous release (`HasDefaultValStr` -> `HasDefaultStr`)
+- Expose `fromSingle` and `fromNested` for when f ~ Identity
+- Expose classes `Build` and `Construct` from `higgledy`
+
 ## 0.3.0.0 [2019.09.16]
 
 - Remove `*With` variants of option constructors and make the `*With` variant behaviour the default
diff --git a/harg.cabal b/harg.cabal
--- a/harg.cabal
+++ b/harg.cabal
@@ -1,7 +1,7 @@
 cabal-version: 2.2
 
 name:           harg
-version:        0.3.0.0
+version:        0.4.0.0
 synopsis:       Haskell program configuration using higher kinded data
 description:    Please see the README on GitHub at <https://github.com/alexpeits/harg#readme>
 homepage:       https://github.com/alexpeits/harg
diff --git a/src/Options/Harg.hs b/src/Options/Harg.hs
--- a/src/Options/Harg.hs
+++ b/src/Options/Harg.hs
@@ -12,10 +12,12 @@
 
   , Single (..)
   , single
+  , fromSingle
 
   , Nested (..)
   , nested
   , getNested
+  , fromNested
 
   , AssocListF (..)
   , (:+)
@@ -82,7 +84,9 @@
 
   -- *** higgledy
   , HKD.HKD
+  , HKD.Build
   , HKD.build
+  , HKD.Construct
   , HKD.construct
   ) where
 
diff --git a/src/Options/Harg/Construct.hs b/src/Options/Harg/Construct.hs
--- a/src/Options/Harg/Construct.hs
+++ b/src/Options/Harg/Construct.hs
@@ -87,7 +87,7 @@
 instance HasDefaultVal ArgumentOpt a where
   defaultVal a o = o { _aDefaultVal = Just a }
 
-class HasDefaultValStr o (attr :: [OptAttr]) where
+class HasDefaultStr o (attr :: [OptAttr]) where
   -- | Add a default unparsed value to an option. Cannot be used in conjuction
   -- with 'defaultVal', 'required' or 'optional'.
   defaultStr
@@ -96,10 +96,10 @@
        )
     => String -> o attr a -> o (OptDefault ': attr) a
 
-instance HasDefaultValStr OptionOpt a where
+instance HasDefaultStr OptionOpt a where
   defaultStr s o = o { _oDefaultStr = Just s }
 
-instance HasDefaultValStr ArgumentOpt a where
+instance HasDefaultStr ArgumentOpt a where
   defaultStr s o = o { _aDefaultStr = Just s }
 
 class HasRequired o (attr :: [OptAttr]) where
@@ -118,7 +118,7 @@
   required o = o { _aDefaultVal = Nothing }
 
 -- | Class for options that can be optional. Cannot be used in conjunction with
--- 'HasDefaultVal', 'HasDefaultValStr' or 'HasRequired'. Note that this will turn a
+-- 'HasDefaultVal', 'HasDefaultStr' or 'HasRequired'. Note that this will turn a
 -- parser for @a@ into a parser for @Maybe a@, modifying the reader function
 -- appropriately.
 -- For example:
diff --git a/src/Options/Harg/Nested.hs b/src/Options/Harg/Nested.hs
--- a/src/Options/Harg/Nested.hs
+++ b/src/Options/Harg/Nested.hs
@@ -9,13 +9,14 @@
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 module Options.Harg.Nested where
 
-import           Data.Coerce      (Coercible, coerce)
-import           Data.Kind        (Type)
-import           GHC.Generics     (Generic)
+import           Data.Coerce           (Coercible, coerce)
+import           Data.Functor.Identity (Identity(..))
+import           Data.Kind             (Type)
+import           GHC.Generics          (Generic)
 
-import qualified Data.Aeson       as JSON
-import qualified Data.Barbie      as B
-import qualified Data.Generic.HKD as HKD
+import qualified Data.Aeson            as JSON
+import qualified Data.Barbie           as B
+import qualified Data.Generic.HKD      as HKD
 
 -- Orphan HKD FromJSON instance
 instance JSON.GFromJSON JSON.Zero (HKD.HKD_ f structure)
@@ -74,6 +75,14 @@
   => Nested b f
   -> f b
 getNested (Nested hkd) = HKD.construct hkd
+
+-- | Helper for when f ~ Identity
+fromNested
+  :: HKD.Construct Identity b
+  => Nested b Identity
+  -> b
+fromNested
+  = runIdentity . getNested
 
 deriving newtype instance Generic (HKD.HKD b f) => Generic (Nested b f)
 deriving newtype instance JSON.FromJSON (HKD.HKD b f) => JSON.FromJSON (Nested b f)
diff --git a/src/Options/Harg/Single.hs b/src/Options/Harg/Single.hs
--- a/src/Options/Harg/Single.hs
+++ b/src/Options/Harg/Single.hs
@@ -5,13 +5,14 @@
 {-# LANGUAGE UndecidableInstances       #-}
 module Options.Harg.Single where
 
-import qualified Data.Functor.Product as P
-import           Data.Kind            (Type)
-import           GHC.Generics         (Generic)
+import           Data.Functor.Identity (Identity(..))
+import qualified Data.Functor.Product  as P
+import           Data.Kind             (Type)
+import           GHC.Generics          (Generic)
 
-import qualified Data.Aeson           as JSON
+import qualified Data.Aeson            as JSON
 
-import qualified Data.Barbie          as B
+import qualified Data.Barbie           as B
 
 
 -- | @Single a f@ is a newtype around @f a@, which allows mixing non-nested
@@ -37,6 +38,10 @@
 -- | Wrap a value into a 'Single'.
 single :: f a -> Single a f
 single = Single
+
+-- | Helper for when f ~ Identity
+fromSingle :: Single a Identity -> a
+fromSingle = runIdentity . getSingle
 
 deriving instance (Show a, Show (f a)) => Show (Single a f)
 deriving newtype instance Generic (f a) => Generic (Single a f)