diff --git a/sample-programs/mono-1.crf b/sample-programs/mono-1.crf
index 9c0a08f..568c674 100644
--- a/sample-programs/mono-1.crf
+++ b/sample-programs/mono-1.crf
@@ -1,6 +1,6 @@
-const x y = x
+const2 x y = x
 
-f x = (const x 'c')
+f x = (const2 x 'c')
 
 main = f 5
 
diff --git a/src/Monomorphizer/Monomorphizer.hs b/src/Monomorphizer/Monomorphizer.hs
index c50a7cc..6c851f9 100644
--- a/src/Monomorphizer/Monomorphizer.hs
+++ b/src/Monomorphizer/Monomorphizer.hs
@@ -91,7 +91,10 @@ isBindMarked ident = gets (Map.member ident)
 
 -- | Finds main bind.
 getMain :: EnvM T.Bind
-getMain = asks (\env -> fromJust $ Map.lookup (T.Ident "main") (input env))
+getMain = asks (\env -> case Map.lookup (T.Ident "main") (input env) of
+                          Just mainBind -> mainBind
+                          Nothing -> error "main not found in monomorphizer!"
+                        )
 
 -- | Makes a kv pair list of polymorphic to monomorphic mappings, throws runtime
 -- error when encountering different structures between the two arguments.
@@ -219,30 +222,24 @@ morphBranch (T.Branch (p, pt) (e, et)) = do
   pt' <- getMonoFromPoly pt
   et' <- getMonoFromPoly et
   env <- ask
-  (p', newLocals)  <- morphPattern pt' (locals env) (p, pt)
-  local (const env { locals = newLocals }) $ do
+  (p', newLocals)  <- morphPattern p pt'
+  local (const env { locals = Set.union (locals env) newLocals }) $ do
     e' <- morphExp et' e
     return $ M.Branch (p', pt') (e', et')
 
--- | Morphs pattern (pattern => expression), gives the newly bound local variables.
-morphPattern :: M.Type -> Set.Set Ident -> (T.Pattern, T.Type) -> EnvM (M.Pattern, Set.Set Ident)
-morphPattern expectedType ls (p, t) = case p of
-  T.PVar ident -> do t' <- getMonoFromPoly t
-                     return (M.PVar (ident, t'), Set.insert ident ls)
-  T.PLit lit ->   do t' <- getMonoFromPoly t
-                     return (M.PLit (convertLit lit, t'), ls)
-  T.PCatch -> return (M.PCatch, ls)
-  -- Constructor ident
-  T.PEnum ident   -> do morphCons expectedType ident
-                        return (M.PEnum ident, ls)
-  T.PInj ident ps -> do morphCons expectedType ident
-                        let (M.TData tIdent ts) = expectedType
-                        -- TODO: this is wrong!
-                        pairs <- mapM (\(pat, patT) -> morphPattern patT ls pat) (zip ps ts)
-                        if length ts == length ps then
-                          return (M.PCatch, Set.singleton $ Ident "$1y")
-                          else return (M.PInj ident (map fst pairs), Set.unions (map snd pairs))
-
+morphPattern :: T.Pattern -> M.Type -> EnvM (M.Pattern, Set.Set Ident)
+morphPattern p expectedType = case p of
+  T.PVar ident     -> return (M.PVar (ident, expectedType), Set.singleton ident)
+  T.PLit lit       -> return (M.PLit (convertLit lit, expectedType), Set.empty)
+  T.PCatch         -> return (M.PCatch, Set.empty)
+  T.PEnum ident    -> do morphCons expectedType ident
+                         return (M.PEnum ident, Set.empty)
+  T.PInj ident pts -> do morphCons expectedType ident
+                         ts' <- mapM (getMonoFromPoly . snd) pts
+                         let pts' = zip (map fst pts) ts'
+                         psSets <- mapM (uncurry morphPattern) pts'
+                         return (M.PInj ident (map fst psSets), Set.unions $ map snd psSets)
+  
 -- | Creates a new identifier for a function with an assigned type.
 newFuncName :: M.Type -> T.Bind -> Ident
 newFuncName t (T.Bind (ident@(Ident bindName), _) _ _) =