diff --git a/aeson-typescript.cabal b/aeson-typescript.cabal
index aead56b..139cbd6 100644
--- a/aeson-typescript.cabal
+++ b/aeson-typescript.cabal
@@ -1,6 +1,6 @@
 cabal-version: 1.12
 
--- This file has been generated from package.yaml by hpack version 0.35.1.
+-- This file has been generated from package.yaml by hpack version 0.36.0.
 --
 -- see: https://github.com/sol/hpack
 
@@ -67,6 +67,7 @@ library
   build-depends:
       aeson
     , base >=4.7 && <5
+    , bytestring
     , containers
     , mtl
     , string-interpolate
diff --git a/package.yaml b/package.yaml
index 3821c55..a1e476d 100644
--- a/package.yaml
+++ b/package.yaml
@@ -35,6 +35,7 @@ tested-with:
 dependencies:
 - aeson
 - base >= 4.7 && < 5
+- bytestring
 - containers
 - mtl
 - string-interpolate
diff --git a/src/Data/Aeson/TypeScript/Formatting.hs b/src/Data/Aeson/TypeScript/Formatting.hs
index 5590433..fea6941 100644
--- a/src/Data/Aeson/TypeScript/Formatting.hs
+++ b/src/Data/Aeson/TypeScript/Formatting.hs
@@ -2,7 +2,9 @@
 
 module Data.Aeson.TypeScript.Formatting where
 
+import Data.Aeson as A
 import Data.Aeson.TypeScript.Types
+import qualified Data.ByteString.Lazy.Char8 as BL8
 import Data.Function ((&))
 import qualified Data.List as L
 import Data.Maybe
@@ -23,15 +25,31 @@ formatTSDeclaration :: FormattingOptions -> TSDeclaration -> String
 formatTSDeclaration (FormattingOptions {..}) (TSTypeAlternatives name genericVariables names maybeDoc) =
   makeDocPrefix maybeDoc <> mainDeclaration
   where
-    mainDeclaration = case typeAlternativesFormat of
+    mainDeclaration = case chooseTypeAlternativesFormat typeAlternativesFormat of
       Enum -> [i|#{exportPrefix exportMode}enum #{typeNameModifier name} { #{alternativesEnum} }|]
+        where
+          alternativesEnum = T.intercalate ", " $ [toEnumName entry | entry <- T.pack <$> names]
       EnumWithType -> [i|#{exportPrefix exportMode}enum #{typeNameModifier name}Enum { #{alternativesEnumWithType} }#{enumType}|]
+        where
+          alternativesEnumWithType = T.intercalate ", " $ [toEnumName entry <> "=" <> entry | entry <- T.pack <$> names]
+          enumType = [i|\n\ntype #{name} = keyof typeof #{typeNameModifier name}Enum;|] :: T.Text
       TypeAlias -> [i|#{exportPrefix exportMode}type #{typeNameModifier name}#{getGenericBrackets genericVariables} = #{alternatives};|]
+        where
+          alternatives = T.intercalate " | " (fmap T.pack names)
+
+    -- Only allow certain formats if some checks pass
+    chooseTypeAlternativesFormat Enum
+      | all isDoubleQuotedString names = Enum
+      | otherwise = TypeAlias
+    chooseTypeAlternativesFormat EnumWithType
+      | all isDoubleQuotedString names = EnumWithType
+      | otherwise = TypeAlias
+    chooseTypeAlternativesFormat x = x
+
+    isDoubleQuotedString s = case A.eitherDecode (BL8.pack s) of
+      Right (A.String _) -> True
+      _ -> False
 
-    alternatives = T.intercalate " | " (fmap T.pack names)
-    alternativesEnum = T.intercalate ", " $ [toEnumName entry | entry <- T.pack <$> names]
-    alternativesEnumWithType = T.intercalate ", " $ [toEnumName entry <> "=" <> entry | entry <- T.pack <$> names]
-    enumType = [i|\n\ntype #{name} = keyof typeof #{typeNameModifier name}Enum;|] :: T.Text
     toEnumName = T.replace "\"" ""
 
 formatTSDeclaration (FormattingOptions {..}) (TSInterfaceDeclaration interfaceName genericVariables (filter (not . isNoEmitTypeScriptField) -> members) maybeDoc) =
diff --git a/test/Formatting.hs b/test/Formatting.hs
index 35ab299..ab3c770 100644
--- a/test/Formatting.hs
+++ b/test/Formatting.hs
@@ -5,7 +5,6 @@ module Formatting (tests) where
 
 import Control.Exception
 import Data.Aeson (defaultOptions)
-import Data.Aeson.TH
 import Data.Aeson.TypeScript.TH
 import Data.Proxy
 import Data.String.Interpolate
@@ -20,7 +19,6 @@ $(deriveTypeScript defaultOptions ''D2)
 
 data Unit = U deriving (Eq, Show)
 $(deriveTypeScript defaultOptions ''Unit)
-$(deriveJSON defaultOptions ''Unit)
 
 data PrimeInType' = PrimeInType
 $(deriveTypeScript defaultOptions ''PrimeInType')
@@ -66,9 +64,11 @@ tests = describe "Formatting" $ do
 
                enum D2 { S2, F2 }|]
 
-      -- it "should generate a TS Enum from unit" $
-      --   formatTSDeclarations' (defaultFormattingOptions { typeAlternativesFormat = Enum }) (getTypeScriptDeclarations @Unit Proxy) `shouldBe`
-      --     [__i|enum Unit { U }|]
+      it "should generate a TS Enum from unit" $
+        formatTSDeclarations' (defaultFormattingOptions { typeAlternativesFormat = Enum }) (getTypeScriptDeclarations @Unit Proxy) `shouldBe`
+          [__i|type Unit = IU;
+
+               type IU = void[];|]
 
     describe "and the EnumWithType format option is set" $
       it "should generate a TS Enum with a type declaration" $