diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Changelog
 
+## [0.8.0.0] - 2024-11-05
+
+* Change `withShownDefault` and `valueWithShown` to accept a function to use in
+  place of `show` rather than a pre-rendered `String`.
+
 ## [0.7.0.1] - 2024-10-27
 
 ### Changed
diff --git a/opt-env-conf.cabal b/opt-env-conf.cabal
--- a/opt-env-conf.cabal
+++ b/opt-env-conf.cabal
@@ -5,7 +5,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           opt-env-conf
-version:        0.7.0.1
+version:        0.8.0.0
 synopsis:       Settings parsing for Haskell: command-line arguments, environment variables, and configuration values.
 homepage:       https://github.com/NorfairKing/opt-env-conf#readme
 bug-reports:    https://github.com/NorfairKing/opt-env-conf/issues
diff --git a/src/OptEnvConf/Parser.hs b/src/OptEnvConf/Parser.hs
--- a/src/OptEnvConf/Parser.hs
+++ b/src/OptEnvConf/Parser.hs
@@ -515,12 +515,12 @@
 --
 -- This does nothing if the parser already has a default value.
 withDefault :: (Show a) => a -> Parser a -> Parser a
-withDefault defaultValue = withShownDefault defaultValue (show defaultValue)
+withDefault = withShownDefault show
 
 -- | Like 'withDefault' but lets you specfiy how to show the default value
 -- yourself.
-withShownDefault :: a -> String -> Parser a -> Parser a
-withShownDefault defaultValue shownDefault = go
+withShownDefault :: (a -> String) -> a -> Parser a -> Parser a
+withShownDefault showDefault defaultValue = go
   where
     go p =
       let p' = p <|> pure defaultValue
@@ -537,7 +537,7 @@
             ParserCommands {} -> p'
             ParserWithConfig {} -> p'
             ParserSetting mLoc s -> case settingDefaultValue s of
-              Nothing -> ParserSetting mLoc $ s {settingDefaultValue = Just (defaultValue, shownDefault)}
+              Nothing -> ParserSetting mLoc $ s {settingDefaultValue = Just (defaultValue, showDefault defaultValue)}
               Just _ -> p
 
 -- | Try a list of parsers in order
diff --git a/src/OptEnvConf/Setting.hs b/src/OptEnvConf/Setting.hs
--- a/src/OptEnvConf/Setting.hs
+++ b/src/OptEnvConf/Setting.hs
@@ -349,11 +349,11 @@
 -- API Note: @default@ is not a valid identifier in Haskell.
 -- I'd also have preferred @default@ instead.
 value :: (Show a) => a -> Builder a
-value a = valueWithShown a (show a)
+value = valueWithShown show
 
--- | Set the default value, along with a shown version of it.
-valueWithShown :: a -> String -> Builder a
-valueWithShown a shown = Builder [BuildSetDefault a shown]
+-- | Set the default value, along with version of it shown by a custom function.
+valueWithShown :: (a -> String) -> a -> Builder a
+valueWithShown show' a = Builder [BuildSetDefault a (show' a)]
 
 -- | Provide an example value for documentation.
 --