diff --git a/src/Compiler/ES/TailRec.idr b/src/Compiler/ES/TailRec.idr
index 105131197..21fe81f9e 100644
--- a/src/Compiler/ES/TailRec.idr
+++ b/src/Compiler/ES/TailRec.idr
@@ -195,16 +195,13 @@ hasTailCalls g (x ::: Nil) = maybe False (contains x) $ lookup x g
 hasTailCalls _ _           = True
 
 -- Given a strongly connected group of functions, plus
--- a unique index, convert them to a list of
--- consisting of the function names plus the `TcGroup`,
--- to which they belong.
+-- a unique index, convert them to the `TcGroup` they belong to.
 toGroup :  SortedMap Name (Name,List Name,NamedCExp)
         -> (Int,List1 Name)
-        -> List (Name,TcGroup)
+        -> TcGroup
 toGroup funMap (groupIndex,functions) =
   let ns    = zipWithIndices $ forget functions
-      group = MkTcGroup groupIndex . fromList $ mapMaybe fun ns
-   in (,group) <$> forget functions
+   in MkTcGroup groupIndex . fromList $ mapMaybe fun ns
   where fun : (Int,Name) -> Maybe (Name,TcFunction)
         fun (fx, n) = do
           (_,args,exp) <- lookup n funMap
@@ -212,16 +209,13 @@ toGroup funMap (groupIndex,functions) =
 
 -- Returns the connected components of the tail call graph
 -- of a set of toplevel function definitions.
--- Every function name that is part of a tail-call group
--- (a set of mutually tail-recursive functions)
--- points to its corresponding group.
-tailCallGroups :  List (Name,List Name,NamedCExp)
-               -> SortedMap Name TcGroup
+-- Every `TcGroup` consists of a set of mutually tail-recursive functions.
+tailCallGroups :  List (Name,List Name,NamedCExp) -> List TcGroup
 tailCallGroups funs =
   let funMap = M.fromList $ map (\t => (fst t,t)) funs
       graph  = map (\(_,_,x) => tailCalls x) funMap
       groups = filter (hasTailCalls graph) $ tarjan graph
-   in fromList $ concatMap (toGroup funMap) (zipWithIndices groups)
+   in map (toGroup funMap) (zipWithIndices groups)
 
 --------------------------------------------------------------------------------
 --          Converting tail call groups to expressions
@@ -319,32 +313,36 @@ convertTcGroup loop g@(MkTcGroup gindex fs) =
 
 -- Tail recursion optimizations: Converts all groups of
 -- mutually tail recursive functions to an imperative loop.
-tailRecOptim :  SortedMap Name TcGroup
+tailRecOptim :  List TcGroup
+             -> (tcOptimized : SortedSet Name)
              -> (tcLoopName : Name)
              -> List (Name,List Name,NamedCExp)
              -> List Function
-tailRecOptim groups loop ts =
+tailRecOptim groups names loop ts =
   let regular = mapMaybe toFun ts
-      tailOpt = concatMap (convertTcGroup loop) $ values groups
+      tailOpt = concatMap (convertTcGroup loop) groups
    in tailOpt ++ regular
 
   where toFun : (Name,List Name,NamedCExp) -> Maybe Function
-        toFun (n,args,exp) = case lookup n groups of
-          Just _  => Nothing
-          Nothing => Just $ MkFunction n args exp
+        toFun (n,args,exp) =
+          if contains n names
+             then Nothing
+             else Just $ MkFunction n args exp
 
 ||| Converts a list of toplevel definitions (potentially
 ||| several groups of mutually tail-recursive functions)
 ||| to a new set of tail-call optimized function definitions.
-||| `MkNmFun`s are converted. Other constructors of `NamedDef`
+||| Only `MkNmFun`s are converted. Other constructors of `NamedDef`
 ||| are ignored and silently dropped.
 export
 functions :  (tcLoopName : Name)
           -> List (Name,FC,NamedDef)
           -> List Function
 functions loop dfs =
-  let ts = mapMaybe def dfs
-   in tailRecOptim (tailCallGroups ts) loop ts
+  let ts     = mapMaybe def dfs
+      groups = tailCallGroups ts
+      names  = SortedSet.fromList $ concatMap (keys . functions) groups
+   in tailRecOptim groups names loop ts
    where def : (Name,FC,NamedDef) -> Maybe (Name,List Name,NamedCExp)
          def (n,_,MkNmFun args x) = Just (n,args,x)
          def _                    = Nothing