diff --git a/Options.hs b/Options.hs
--- a/Options.hs
+++ b/Options.hs
@@ -71,7 +71,7 @@
            in  parseri { infoParser = injectDefaultP env (path ++ [normalizeName cmd]) (infoParser parseri) }
      in  OptP (Option (CmdReader cmds (`M.lookup` cmdMap)) props)
   | (Option (OptReader names (CReader _ rdr) _) _) <- o =
-     p <|> either (const empty) pure (msum $ map (rdr <=< (maybe (Left $ ErrorMsg "Missing environment variable") Right . getEnvValue env path)) names)
+     p <|> either' (const empty) pure (msum $ map (rdr <=< (maybe (left $ ErrorMsg "Missing environment variable") right . getEnvValue env path)) names)
   | (Option (FlagReader names a) _) <- o =
      p <|> if any ((==Just "1") . getEnvValue env path) names then pure a else empty
   | otherwise = p
@@ -80,6 +80,16 @@
 injectDefaultP env path (AltP p1 p2) =
    AltP (injectDefaultP env path p1) (injectDefaultP env path p2)
 injectDefaultP _env _path b@(BindP {}) = b
+
+#if MIN_VERSION_optparse_applicative(0,6,0)
+right = ReadM . Right
+left = ReadM . Left
+either' f g (ReadM x) = either f g x
+#else
+right = Right
+left = Left
+either' = either
+#endif
 
 getEnvValue :: M.Map [String] String -> [String] -> OptName -> Maybe String
 getEnvValue env path (OptLong l) = M.lookup (path ++ [normalizeName l]) env
diff --git a/main.hs b/main.hs
--- a/main.hs
+++ b/main.hs
@@ -16,6 +16,9 @@
 import           Scaffolding.Scaffolder
 
 import           Options.Applicative.Builder.Internal (Mod, OptionFields)
+#if MIN_VERSION_optparse_applicative(0,6,0)
+import           Options.Applicative.Types (ReadM (ReadM))
+#endif
 
 #ifndef WINDOWS
 import           Build                  (touch)
@@ -165,7 +168,11 @@
 optStr m =
     nullOption $ value Nothing <> reader (success . str)  <> m
   where
+#if MIN_VERSION_optparse_applicative(0,6,0)
+    success = ReadM . Right
+#else
     success = Right
+#endif
 
 -- | Like @rawSystem@, but exits if it receives a non-success result.
 rawSystem' :: String -> [String] -> IO ()
diff --git a/yesod-bin.cabal b/yesod-bin.cabal
--- a/yesod-bin.cabal
+++ b/yesod-bin.cabal
@@ -1,5 +1,5 @@
 name:            yesod-bin
-version:         1.2.3.3
+version:         1.2.3.4
 license:         MIT
 license-file:    LICENSE
 author:          Michael Snoyman <michael@snoyman.com>