diff --git a/src/Options.hs b/src/Options.hs
index da7f031..af74f91 100644
--- a/src/Options.hs
+++ b/src/Options.hs
@@ -1,4 +1,4 @@
-module Options (Package(..), Options(..), def, Packages, options) where
+module Options (Package(..), Options(..), OutputForm(..), def, Packages(Packages), options) where
 import Prelude hiding (takeWhile, writeFile)
 
 import Constants
@@ -23,14 +23,27 @@ import System.Exit (exitWith)
 import System.IO (stderr)
 import Text.StringTemplate (newSTMP, render, setAttribute, StringTemplate)
 
+data OutputForm = Traditional
+                | Flake
+     deriving (Eq, Show)
+
+newtype Packages = Packages [ Package ] deriving Show
+
+
 type Package = Text
-type Packages = [ Package ]
+
+instance Eq Packages where
+  Packages a == Packages b = sort a == sort b
+
+packageList = toPackageList . packages
+  where toPackageList (Packages p) = p
+
 data Options = Options {
     packages :: Packages
   , command :: Maybe Text
-  , generateFlake :: Bool
+  , outputForm :: !OutputForm
   , prioritiseLocalPinnedSystem :: Bool
-}
+} deriving (Eq, Show)
 
 data OptionsParser = OptionsParser [Text] -- remainingOptions
                                    (Either Text (Options -> Options)) -- result
@@ -47,7 +60,7 @@ options progName args =
                let (OptionsParser newRemaining newRes) = f hd tl
                in worker $ OptionsParser newRemaining ((.) <$> newRes <*> res)
 
-      screenForNoPackages (Right opts) | null (packages opts) = Left noPackagesError
+      screenForNoPackages (Right opts) | null (packageList opts) = Left noPackagesError
       screenForNoPackages anyThingElse = anyThingElse
       initialArgumentsToParse = shellArgFilter args
       initialModifier = Right $ if hasShellArg args then setFlakeGeneration else id
@@ -66,7 +79,7 @@ options progName args =
         baseOption :: Text -> [Text] -> OptionsParser
         baseOption "-h" = returnError $ helpText progName
         baseOption "--help" = returnError $ helpText progName
-        baseOption "--version" = returnError $ "Shellify " <> (pack $ showVersion version)
+        baseOption "--version" = returnError $ "Shellify " <> pack ( showVersion version)
         baseOption "--command" = handleCommandSwitch
         baseOption "--run" = handleCommandSwitch
         baseOption "--with-flake" = transformOptionsWith setFlakeGeneration
@@ -81,13 +94,15 @@ options progName args =
                                     = transformOptionsWith (setCommand hd) tl
         handleCommandSwitch [] = returnError "Argument missing to switch" []
 
-        appendPackages ps opts = opts{packages=ps ++ packages opts}
+        appendPackages ps opts = opts{
+          packages = Packages (ps ++ packageList opts)
+        }
         setCommand cmd opts = opts{command=Just cmd}
-        setFlakeGeneration opts = opts{generateFlake=True}
+        setFlakeGeneration opts = opts{outputForm=Flake}
         setPrioritiseLocalPinnedSystem opts = opts {prioritiseLocalPinnedSystem=True}
         returnError errorText remaining = OptionsParser remaining $ Left errorText
 
-consumePackageArgs :: [Text] -> (Packages, [Text])
+consumePackageArgs :: [Text] -> ([Package], [Text])
 consumePackageArgs = worker []
   where worker pkgs [] = (pkgs, [])
         worker pkgs options@(hd:_) | isSwitch hd
@@ -102,10 +117,4 @@ hasShellArg (hd:tl) | isSwitch hd = hasShellArg tl
 isSwitch = isPrefixOf "-"
 
 instance Default Options where
-  def = Options [] Nothing False False
-
-instance Eq Options where
-  a == b =  isEqual command
-         && isEqual (sort . packages)
-         && isEqual generateFlake
-    where isEqual f = f a == f b
+  def = Options (Packages []) Nothing Traditional False
diff --git a/src/TemplateGeneration.hs b/src/TemplateGeneration.hs
index 3d42b5f..1574120 100644
--- a/src/TemplateGeneration.hs
+++ b/src/TemplateGeneration.hs
@@ -17,7 +17,7 @@ import Text.ParserCombinators.Parsec (Parser, char, endBy, eof, many1, noneOf, p
 import Text.StringTemplate (newSTMP, render, setAttribute)
 
 generateFlakeText :: Text -> Options -> Maybe Text
-generateFlakeText db Options{packages=packages, generateFlake=shouldGenerateFlake, prioritiseLocalPinnedSystem=prioritiseLocalPinnedSystem} =
+generateFlakeText db Options{packages=Packages packages, outputForm=outputForm, prioritiseLocalPinnedSystem=prioritiseLocalPinnedSystem} =
   bool
     Nothing
     (Just $ render
@@ -26,7 +26,7 @@ generateFlakeText db Options{packages=packages, generateFlake=shouldGenerateFlak
           $ setAttribute "pkgs_decls" pkgsDecls
           $ setAttribute "shell_args" shellArgs
           $ newSTMP flakeTemplate)
-    shouldGenerateFlake
+    (outputForm == Flake)
   where repos = getPackageRepoWrapper packages
         repoVars = getPackageRepoVarName <$> repos
         repoInputs = repoInput <$> repos
@@ -42,7 +42,7 @@ generateFlakeText db Options{packages=packages, generateFlake=shouldGenerateFlak
         shellArgs = (\(a,b) -> a <> "=" <> b <> ";") <$> zip repoVars pkgsVars 
 
 generateShellDotNixText :: Options -> Text
-generateShellDotNixText Options{packages=packages, command=command} =
+generateShellDotNixText Options{packages=Packages packages, command=command} =
   render
   $ setAttribute "build_inputs" pkgs
   $ setAttribute "parameters" parameters
diff --git a/test/Spec.hs b/test/Spec.hs
index ca6c4bf..45d048a 100644
--- a/test/Spec.hs
+++ b/test/Spec.hs
@@ -45,17 +45,17 @@ main = hspec $ do
       it "allows a command to be specified with a package" $
         theOptions "-p python --command cowsay"
           `shouldBe`
-        Right def{packages=["python"], command=Just "cowsay"}
+        Right def{packages=Packages ["python"], command=Just "cowsay"}
 
       it "allows a command to be specified before a package" $
         theOptions "--run cowsay -p python"
           `shouldBe`
-        Right def{packages=["python"], command=Just "cowsay"}
+        Right def{packages=Packages ["python"], command=Just "cowsay"}
 
       it "allows a command to be specified before and after a package" $
         theOptions "-p cowsay --command cowsay -p python"
           `shouldBe`
-        Right def{packages=[ "cowsay", "python" ], command=Just "cowsay"}
+        Right def{packages=Packages [ "cowsay", "python" ], command=Just "cowsay"}
 
       it "fails if command has no argument" $ do
         shellifyWithArgs "--command -p python"
@@ -96,7 +96,7 @@ main = hspec $ do
     it "supports new shell commands" $
       theOptions "shell nixpkgs#python nixpkgs#cowsay"
         `shouldBe`
-      Right def{packages=[ "nixpkgs#python", "nixpkgs#cowsay" ], generateFlake=True}
+      Right def{packages=Packages [ "nixpkgs#python", "nixpkgs#cowsay" ], outputForm=Flake}
 
   describe "When dealing with multiple source repositories it should produce the correct output files for" $ do
 
diff --git a/test/TestHelpers.hs b/test/TestHelpers.hs
index 2b928c8..f75dbcf 100644
--- a/test/TestHelpers.hs
+++ b/test/TestHelpers.hs
@@ -129,12 +129,10 @@ shouldResultInPackages :: Text -> [Text] -> Expectation
 shouldResultInPackages parameters packages =
      theOptions parameters
        `shouldBe`
-     Right def{packages=packages}
+     Right def{packages=Packages packages}
 
 theOptions = options "nix-shellify" . words
 
-instance Show Options
-
 readNixTemplate :: FilePath -> IO Text
 readNixTemplate fileName =
     stripTrailingNewline <$> readFile ("test/outputs/" <> fileName)