diff --git a/src/Lish/Eval.hs b/src/Lish/Eval.hs
index eedb5a8..e75a5eb 100644
--- a/src/Lish/Eval.hs
+++ b/src/Lish/Eval.hs
@@ -31,18 +31,21 @@ infer ctx (List (expr:exprs)) = do
       Right _     -> return $ LList t
 infer ctx (Atom a) = case Map.lookup a ctx of
   Just t  -> return t
-  Nothing -> return LAtom
-infer ctx (Fn params body _ types) = do
-  let newCtx = Map.union ctx (Map.frommList (zip params (fst types)))
-  check newCtx body (snd type) >>= return $ LFn (fst types) (snd types)
-infer ctx (Lambda (Fn params _ _ (ptypes,retType)):exprs) =
-  if length params /= length exprs
+  Nothing -> Left . TypeError $ "Undefined atom: " <> toS a
+infer ctx (Fn parameters fnbody _ (ptypes,retType)) = do
+  let newCtx = Map.union ctx (Map.fromList (zip parameters ptypes))
+  checkType newCtx fnbody retType
+  return $ LFn ptypes retType
+infer ctx (Lambda ((Fn fnparams _ _ (ptypes,retType)):exprs)) =
+  if length fnparams /= length exprs
   then Left (TypeError "Fn applied to the wrong number of parameters")
   else do
-    types <- map (infer ctx) params
-    if types /= ptypes
-      then Left (TypeError ("Expected " <> show ptypes <> " bug got " <> types))
+    inferedTypes <- mapM (infer ctx) exprs
+    if inferedTypes /= ptypes
+      then Left . TypeError $ "Expected " <> show ptypes
+                              <> " bug got " <> show inferedTypes
       else return retType
+infer _ (Lambda _) = Left . TypeError $ "First element of a lambda must be a Fn or a Command"
 infer _ sexp = Left . TypeError $ "can't infer the type of " <> show sexp
 
 -- | Check the type of some expression regarding a type context
@@ -83,7 +86,7 @@ reduceLambda (Lambda (expr:exprs)) = do
                 Nothing -> do
                   reducedArgs <- mapM reduceLambda exprs
                   executeShell (Lambda ((Atom f):reducedArgs))
-        f@(Fn _ _ _) -> applyFn f exprs
+        f@(Fn _ _ _ _) -> applyFn f exprs
         s  -> do
           reducedArgs <- mapM reduceLambda exprs
           executeShell (Lambda (s:reducedArgs))
@@ -95,7 +98,7 @@ reduceLambda (Atom x) = do
 reduceLambda x          = return x
 
 applyFn :: SExp -> ReduceUnawareCommand
-applyFn (Fn par bod clos) args =
+applyFn (Fn par bod clos _) args =
   if length par /= length args
     then shellErr "wrong number of arguments"
     else do
@@ -112,8 +115,8 @@ tryEnvCommand :: Text -> [SExp] -> StateT Env IO (Maybe SExp)
 tryEnvCommand f args = do
   envcmd <- get
   case Map.lookup f envcmd of
-    Just fn@(Fn _ _ _) -> Just <$> (applyFn fn args)
-    _                  -> return Nothing
+    Just fn@(Fn _ _ _ _) -> Just <$> (applyFn fn args)
+    _                    -> return Nothing
 
 
 tryInternalCommand :: Text -> [SExp] -> StateT Env IO (Maybe SExp)
diff --git a/src/Lish/InternalCommands.hs b/src/Lish/InternalCommands.hs
index dbdea0b..ece0206 100644
--- a/src/Lish/InternalCommands.hs
+++ b/src/Lish/InternalCommands.hs
@@ -134,6 +134,7 @@ fn reducer (p:bodies) = do
         then return (Fn { params = catMaybes parameters
                         , body = Lambda $ (Atom "do"):bodies
                         , closure = mempty
+                        , types = ([],LCommand)
                         })
         else return Void
     _ -> return Void
diff --git a/src/Lish/Types.hs b/src/Lish/Types.hs
index c9cf98a..4c964ca 100644
--- a/src/Lish/Types.hs
+++ b/src/Lish/Types.hs
@@ -38,7 +38,7 @@ data SExp = Atom Text
           | WaitingStream CmdStream
           deriving (Eq,Show)
 
-data LishType = LAtom
+data LishType = LCommand
               | LNum
               | LBool
               | LStr
@@ -57,7 +57,7 @@ repr (Str s)           = "\"" <> toS s <> "\""
 repr (List sexprs)     = "[" <> (Text.intercalate " " (map repr sexprs)) <> "]"
 repr (Lambda sexprs)   = "(" <> (Text.intercalate " " (map repr sexprs)) <> ")"
 repr Void              = "ε"
-repr (Fn p _ _)        = "(λ" <> (Text.intercalate "." p) <> ". ... )"
+repr (Fn p _ _ _)      = "(λ" <> (Text.intercalate "." p) <> ". ... )"
 repr (Stream _)        = "<stream>"
 repr (WaitingStream _) = "<w-stream>"