diff --git a/src/Data/NestTuple/TH.hs b/src/Data/NestTuple/TH.hs
--- a/src/Data/NestTuple/TH.hs
+++ b/src/Data/NestTuple/TH.hs
@@ -1,3 +1,5 @@
+{-# LANGUAGE CPP #-}
+
 module Data.NestTuple.TH where
 
 
@@ -14,8 +16,15 @@
 mkPairT :: Type -> Type -> Type
 mkPairT a b = foldl AppT (TupleT 2) [a,b]
 
+mkTupE :: [Exp] -> Exp
+#if __GLASGOW_HASKELL__ >= 810
+mkTupE = TupE . map Just
+#else
+mkTupE = TupE
+#endif
+
 mkPairE :: Exp -> Exp -> Exp
-mkPairE a b = TupE [a,b]
+mkPairE a b = mkTupE [a,b]
 
 mkPairP :: Pat -> Pat -> Pat
 mkPairP a b = TupP [a,b]
@@ -64,7 +73,7 @@
         , FunD (mkName "unnest")
             [ Clause
                 [foldNest VarP mkPairP $ toNest vars]
-                (NormalB (TupE (map VarE vars)))
+                (NormalB (mkTupE (map VarE vars)))
                 []
             ]
         ]
diff --git a/src/Language/Syntactic/TH.hs b/src/Language/Syntactic/TH.hs
--- a/src/Language/Syntactic/TH.hs
+++ b/src/Language/Syntactic/TH.hs
@@ -232,9 +232,12 @@
 classPred cl con = ClassP cl
 #endif
 
--- | Portable method for constructing a type synonym instances
+-- | Portable method for constructing a type synonym instance
 tySynInst :: Name -> [Type] -> Type -> Dec
-#if __GLASGOW_HASKELL__ >= 708
+#if __GLASGOW_HASKELL__ >= 808
+tySynInst t as rhs = TySynInstD $
+  TySynEqn Nothing (foldl AppT (ConT t) as) rhs
+#elif __GLASGOW_HASKELL__ >= 708
 tySynInst t as rhs = TySynInstD t (TySynEqn as rhs)
 #else
 tySynInst = TySynInstD
diff --git a/syntactic.cabal b/syntactic.cabal
--- a/syntactic.cabal
+++ b/syntactic.cabal
@@ -1,5 +1,5 @@
 Name:           syntactic
-Version:        3.8.1
+Version:        3.8.2
 Synopsis:       Generic representation and manipulation of abstract syntax
 Description:    The library provides a generic representation of type-indexed abstract syntax trees
                 (or indexed data types in general). It also permits the definition of open syntax
@@ -83,8 +83,8 @@
       Language.Syntactic.Sugar.TupleTyped
 
   build-depends:
-    base >= 4.6 && < 4.13,
-    constraints < 0.11,
+    base >= 4.6 && < 4.15,
+    constraints < 0.13,
     containers < 0.7,
     data-hash < 0.3,
     deepseq < 1.5,
diff --git a/tests/AlgorithmTests.hs b/tests/AlgorithmTests.hs
--- a/tests/AlgorithmTests.hs
+++ b/tests/AlgorithmTests.hs
@@ -25,6 +25,9 @@
 
 
 
+subCap :: (Num a, Ord a) => a -> a -> a
+subCap a b = max 0 (a - b)
+
 data Sym sig
   where
     Int   :: Int -> Sym (Full Int)
@@ -101,10 +104,11 @@
     ]
 
 genExp :: Int -> [Name] -> Gen (ASTF Dom Int)
+genExp s _ | s < 0 = error (show s)
 genExp s inScope = frequency
     [ (1, fmap int arbitrary)
     , (1, fmap varr $ genVar 1 1 inScope)
-    , (s, do a <- genExp (s-1) inScope
+    , (s, do a <- genExp (s `subCap` 1) inScope
              return $ neg a
       )
     , (s, do a <- genExp (s `div` 2) inScope
@@ -131,14 +135,14 @@
 genExp1 :: Int -> [Name] -> Gen (ASTF Dom (Int -> Int))
 genExp1 s inScope = do
     v    <- genVar 1 2 inScope
-    body <- genExp (s-1) (v:inScope)
+    body <- genExp (s `subCap` 1) (v:inScope)
     return $ lamm v body
 
 genExp2 :: Int -> [Name] -> Gen (ASTF Dom (Int -> Int -> Int))
 genExp2 s inScope = do
     v1   <- genVar 1 2 inScope
     v2   <- genVar 1 2 (v1:inScope)
-    body <- genExp (s-2) (v2:v1:inScope)
+    body <- genExp (s `subCap` 2) (v2:v1:inScope)
     return $ lamm v1 $ lamm v2 body
 
 genExp3 :: Int -> [Name] -> Gen (ASTF Dom (Int -> Int -> Int -> Int))
@@ -146,7 +150,7 @@
     v1   <- genVar 1 2 inScope
     v2   <- genVar 1 2 (v1:inScope)
     v3   <- genVar 1 2 (v2:v1:inScope)
-    body <- genExp (s-3) (v3:v2:v1:inScope)
+    body <- genExp (s `subCap` 3) (v3:v2:v1:inScope)
     return $ lamm v1 $ lamm v2 $ lamm v3 body
 
 shrinkExp :: AST Dom sig -> [AST Dom sig]