diff --git a/Data/Yoko/TH.hs b/Data/Yoko/TH.hs
--- a/Data/Yoko/TH.hs
+++ b/Data/Yoko/TH.hs
@@ -83,7 +83,6 @@
 import qualified Control.Monad.Trans as Trans
 
 import qualified Control.Arrow as Arrow
-import Control.Monad ((<=<))
 
 import Data.Set (Set)
 import qualified Data.Set as Set
@@ -233,7 +232,7 @@
 
 fieldRO :: [(Int, Mapping)] -> Set Name -> Type -> Q (Type, FieldRO)
 fieldRO maps bg = w' where
-  w' = uncurry w <=< uncurry expandSyn . peelApp
+  w' = uncurry w . peelApp
 
   isRec n = Set.member n bg
 
@@ -246,9 +245,13 @@
     AppT{}              -> Int.thFail $ "impossible: AppT is guarded by peelApp."
     SigT ty _           -> uncurry w $ peelAppAcc tys ty
     ForallT{}           -> Int.thFail $ "no support for ForallT."
-    ConT n
-      | isRec n -> if not (null recs) then Int.thFail "does not support nested recursion."
-                   else simple True ty tys
+    ConT n | isRec n -> do
+      rhs <- expandSyn ty tys
+      case rhs of
+        Just (ty, tys) -> w ty tys
+        Nothing ->
+          if not (null recs) then Int.thFail "no support for nested recursion."
+          else simple True ty tys
     _ 
       | not (null recs) -> case lookup (length recs) maps of
         Nothing -> Int.thFail $ "no case in the given YokoOptions for type constructors with " ++ show (length recs) ++ " arguments."
diff --git a/Data/Yoko/TH/Internal.hs b/Data/Yoko/TH/Internal.hs
--- a/Data/Yoko/TH/Internal.hs
+++ b/Data/Yoko/TH/Internal.hs
@@ -3,6 +3,7 @@
 module Data.Yoko.TH.Internal where
 
 import Data.Maybe (fromMaybe)
+import Control.Monad (mplus)
 
 import Language.Haskell.TH
 
@@ -49,14 +50,18 @@
 
 
 
-expandSyn :: Type -> [Type] -> Q (Type, [Type])
-expandSyn ty@(ConT n) tys = do
+expandSyn :: Type -> [Type] -> Q (Maybe (Type, [Type]))
+expandSyn (ConT n) tys = do
   i <- reify n
   case i of
     TyConI (TySynD _ (map tvbName -> formals) rhs) ->
-      uncurry expandSyn $ peelApp $ msubst (zip formals tys) rhs
-    _ -> return (ty, tys)
-expandSyn ty tys = return (ty, tys)
+      -- formals <= tys because type synonyms must be fully applied.
+      -- peelAppAcc handles both formals < tys and formals == tys.
+      let tytys = peelAppAcc (drop (length formals) tys) $
+                  msubst (zip formals tys) rhs
+      in (`mplus` Just tytys) `fmap` uncurry expandSyn tytys
+    _ -> return Nothing
+expandSyn _ _ = return Nothing
 
 
 
diff --git a/yoko.cabal b/yoko.cabal
--- a/yoko.cabal
+++ b/yoko.cabal
@@ -1,5 +1,5 @@
 name: yoko
-version: 0.3.2.1
+version: 0.3.2.2
 synopsis: Generic Programming with Disbanded Data Types
 
 description: