diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,8 +3,14 @@
 `elm-street` uses [PVP Versioning][1].
 The changelog is available [on GitHub][2].
 
-0.0.0
-=====
+## 0.0.1 — Mar 29, 2019
+
+* [#64](https://github.com/holmusk/elm-street/issues/64):
+  Fix indentation for the generated enums.
+* [#66](https://github.com/holmusk/elm-street/issues/66):
+  Patch JSON encoders and decoders for sum types with a single field.
+
+## 0.0.0
 
 * Initially created.
 
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -182,7 +182,7 @@
     { userName :: Text
     , userAge  :: Int
     } deriving (Generic)
-      deriving anyclass (Elm)
+      deriving (Elm, ToJSON, FromJSON) via ElmStreet User
 ```
 
 **Elm**
@@ -215,7 +215,7 @@
     | Rejected
     | Reviewing
     deriving (Generic)
-    deriving anyclass (Elm)
+    deriving (Elm, ToJSON, FromJSON) via ElmStreet RequestStatus
 ```
 
 **Elm**
@@ -257,6 +257,7 @@
 newtype Age = Age
     { unAge :: Int
     } deriving (Generic)
+      deriving newtype (FromJSON, ToJSON)
       deriving anyclass (Elm)
 ```
 
@@ -279,7 +280,10 @@
 **Haskell**
 
 ```haskell
-newtype Id a = Id { unId :: Text }
+newtype Id a = Id
+    { unId :: Text
+    } deriving (Generic)
+      deriving newtype (FromJSON, ToJSON)
 
 instance Elm (Id a) where
     toElmDefinition _ = elmNewtype @Text "Id" "unId"
@@ -309,7 +313,7 @@
     | Visitor Text
     | Blocked
     deriving (Generic)
-    deriving anyclass (Elm)
+    deriving (Elm, ToJSON, FromJSON) via ElmStreet Guest
 ```
 
 **Elm**
@@ -323,7 +327,7 @@
 encodeGuest : Guest -> Value
 encodeGuest x = E.object <| case x of
     Regular x1 x2 -> [("tag", E.string "Regular"), ("contents", E.list identity [E.string x1, E.int x2])]
-    Visitor x1 -> [("tag", E.string "Visitor"), ("contents", E.list identity [E.string x1])]
+    Visitor x1 -> [("tag", E.string "Visitor"), ("contents", E.string x1)]
     Blocked  -> [("tag", E.string "Blocked"), ("contents", E.list identity [])]
 
 decodeGuest : Decoder Guest
@@ -331,7 +335,7 @@
     let decide : String -> Decoder Guest
         decide x = case x of
             "Regular" -> D.field "contents" <| D.map2 Regular (D.index 0 D.string) (D.index 1 D.int)
-            "Visitor" -> D.field "contents" <| D.map Visitor (D.index 0 D.string)
+            "Visitor" -> D.field "contents" <| D.map Visitor D.string
             "Blocked" -> D.succeed Blocked
             c -> D.fail <| "Guest doesn't have such constructor: " ++ c
     in D.andThen decide (D.field "tag" D.string)
diff --git a/elm-street.cabal b/elm-street.cabal
--- a/elm-street.cabal
+++ b/elm-street.cabal
@@ -1,6 +1,6 @@
 cabal-version:       2.0
 name:                elm-street
-version:             0.0.0
+version:             0.0.1
 synopsis:            Crossing the road between Haskell and Elm
 description:
     `Elm-street` allows you to generate automatically derived from Haskell types
@@ -34,7 +34,7 @@
                          Elm.Print
 
   build-depends:       base >= 4.11.1.0 && < 4.13
-                     , aeson >= 1.4
+                     , aeson >= 1.3
                      , directory ^>= 1.3
                      , filepath ^>= 1.4
                      , prettyprinter ^>= 1.2.1
@@ -128,10 +128,10 @@
   other-modules:       Api
 
   build-depends:       base
-                     , servant ^>= 0.15
-                     , servant-server ^>= 0.15
+                     , servant >= 0.14 && < 0.17
+                     , servant-server >= 0.14 && < 0.17
                      , types
-                     , wai ^>= 3.2.2
+                     , wai ^>= 3.2
                      , warp ^>= 3.2
 
   ghc-options:         -Wall
diff --git a/src/Elm/Aeson.hs b/src/Elm/Aeson.hs
--- a/src/Elm/Aeson.hs
+++ b/src/Elm/Aeson.hs
@@ -1,3 +1,5 @@
+{-# OPTIONS_GHC -fno-warn-redundant-constraints #-}
+
 {-# LANGUAGE AllowAmbiguousTypes  #-}
 {-# LANGUAGE FlexibleContexts     #-}
 {-# LANGUAGE UndecidableInstances #-}
diff --git a/src/Elm/Print.hs b/src/Elm/Print.hs
--- a/src/Elm/Print.hs
+++ b/src/Elm/Print.hs
@@ -25,7 +25,7 @@
 
 import Data.List.NonEmpty (NonEmpty ((:|)), toList)
 import Data.Text (Text)
-import Data.Text.Prettyprint.Doc (Doc, brackets, colon, comma, concatWith, dquotes, emptyDoc,
+import Data.Text.Prettyprint.Doc (Doc, align, brackets, colon, comma, concatWith, dquotes, emptyDoc,
                                   equals, lbrace, lbracket, line, lparen, nest, parens, pipe,
                                   pretty, prettyList, rbrace, rbracket, rparen, sep, space,
                                   surround, vsep, (<+>))
@@ -263,7 +263,7 @@
 elmEnumUniverse t@ElmType{..} = vsep
     -- function type
     [ universeName <+> colon <+> "List" <+> pretty elmTypeName
-    , universeName <+> equals <+> prettyList (getConstructorNames t)
+    , universeName <+> equals <+> align (prettyList $ getConstructorNames t)
     ]
   where
     universeName :: Doc ann
@@ -346,8 +346,14 @@
             map (pretty . mkText "x") [1..]
 
         contents :: Doc ann
-        contents = "," <+> parens (dquotes "contents" <> comma <+> "E.list identity" <+> brackets fieldEncs)
+        contents = "," <+> parens (dquotes "contents" <> comma <+> contentsEnc)
 
+        -- JSON encoder for the "contents" key
+        contentsEnc :: Doc ann
+        contentsEnc = case elmConstructorFields of
+            [_] -> fieldEncs
+            _   -> "E.list identity" <+> brackets fieldEncs
+
         -- | @encoderA x1@
         fieldEncs :: Doc ann
         fieldEncs = concatWith (surround ", ") $
@@ -581,10 +587,10 @@
 
     cases :: ElmConstructor -> Doc ann
     cases ElmConstructor{..} = dquotes cName <+> arrow <+>
-        case length elmConstructorFields of
-            0 -> "D.succeed" <+> cName
-            n -> "D.field \"contents\" <| D.map" <> mapNum n <+> cName <+> createIndexes
-
+        case elmConstructorFields of
+            []  -> "D.succeed" <+> cName
+            [f] -> "D.field \"contents\" <| D.map" <+> cName <+> typeRefDecoder f
+            l   -> "D.field \"contents\" <| D.map" <> mapNum (length l) <+> cName <+> createIndexes
       where
         cName :: Doc ann
         cName = pretty elmConstructorName
@@ -672,4 +678,7 @@
 putStrLn $ T.unpack $ prettyShowDefinition $ DefType $ ElmType "Status" [] $ (ElmConstructor "Approved" [TypeName "String", TypeName "Int"]) :| [ElmConstructor  "Yoyoyo" [], ElmConstructor "Wow" [TypeName "a"]]
 
 putStrLn $ T.unpack $ prettyShowDefinition $ DefType $ ElmType "Status" ["a"] $ (ElmConstructor "Approved" [TypeName "String", TypeName "Int"]) :| [ElmConstructor  "Yoyoyo" [], ElmConstructor "Wow" [TypeName "a"]]
+
+putStrLn $ T.unpack $ prettyShowDefinition $ DefType $ ElmType "Status" [] ((ElmConstructor "Approved" []) :| [ElmConstructor  "Yoyoyo" [], ElmConstructor "Wow" [], ElmConstructor "OneMore" [], ElmConstructor "AndAnother" []])
+
 -}
diff --git a/types/Types.hs b/types/Types.hs
--- a/types/Types.hs
+++ b/types/Types.hs
@@ -34,17 +34,17 @@
 
 
 data Prims = Prims
-    { primsUnit   :: ()
-    , primsBool   :: Bool
-    , primsChar   :: Char
-    , primsInt    :: Int
-    , primsFloat  :: Double
-    , primsString :: String
-    , primsTime   :: UTCTime
-    , primsMaybe  :: Maybe Word
-    , primsResult :: Either Int String
-    , primsPair   :: (Char, Bool)
-    , primsList   :: [Int]
+    { primsUnit   :: !()
+    , primsBool   :: !Bool
+    , primsChar   :: !Char
+    , primsInt    :: !Int
+    , primsFloat  :: !Double
+    , primsString :: !String
+    , primsTime   :: !UTCTime
+    , primsMaybe  :: !(Maybe Word)
+    , primsResult :: !(Either Int String)
+    , primsPair   :: !(Char, Bool)
+    , primsList   :: ![Int]
     } deriving (Generic, Eq, Show)
 #if ( __GLASGOW_HASKELL__ >= 806 )
       deriving (Elm, ToJSON, FromJSON) via ElmStreet Prims
@@ -77,10 +77,10 @@
     deriving anyclass (Elm, FromJSON, ToJSON)
 
 data User = User
-    { userId     :: Id User
-    , userName   :: Text
-    , userAge    :: Age
-    , userStatus :: RequestStatus
+    { userId     :: !(Id User)
+    , userName   :: !Text
+    , userAge    :: !Age
+    , userStatus :: !RequestStatus
     } deriving (Generic, Eq, Show)
       deriving anyclass (Elm)
 
@@ -95,9 +95,9 @@
     deriving anyclass (Elm, FromJSON, ToJSON)
 
 data UserRequest = UserRequest
-    { userRequestIds     :: [Id User]
-    , userRequestLimit   :: Word32
-    , userRequestExample :: Maybe (Either User Guest)
+    { userRequestIds     :: ![Id User]
+    , userRequestLimit   :: !Word32
+    , userRequestExample :: !(Maybe (Either User Guest))
     } deriving (Generic, Eq, Show)
       deriving anyclass (Elm)
 
@@ -106,13 +106,13 @@
 
 -- | All test types together in one type to play with.
 data OneType = OneType
-    { oneTypePrims         :: Prims
-    , oneTypeId            :: Id OneType
-    , oneTypeAge           :: Age
-    , oneTypeRequestStatus :: RequestStatus
-    , oneTypeUser          :: User
-    , oneTypeGuest         :: Guest
-    , oneTypeUserRequest   :: UserRequest
+    { oneTypePrims         :: !Prims
+    , oneTypeId            :: !(Id OneType)
+    , oneTypeAge           :: !Age
+    , oneTypeRequestStatus :: !RequestStatus
+    , oneTypeUser          :: !User
+    , oneTypeGuests        :: ![Guest]
+    , oneTypeUserRequest   :: !UserRequest
     } deriving (Generic, Eq, Show)
       deriving anyclass (Elm)
 
@@ -139,7 +139,7 @@
     , oneTypeAge = Age 18
     , oneTypeRequestStatus = Reviewing
     , oneTypeUser = User (Id "1") "not-me" (Age 100) Approved
-    , oneTypeGuest = Regular "nice" 7
+    , oneTypeGuests = [guestRegular, guestVisitor, guestBlocked]
     , oneTypeUserRequest = defaultUserRequest
     }
   where
@@ -157,6 +157,11 @@
         , primsPair   = ('o', False)
         , primsList   = [1..5]
         }
+
+    guestRegular, guestVisitor, guestBlocked :: Guest
+    guestRegular = Regular "nice" 7
+    guestVisitor = Visitor "new-guest"
+    guestBlocked = Blocked
 
     defaultUserRequest :: UserRequest
     defaultUserRequest = UserRequest