diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,9 @@
 # Revision history for th-extras
 
+## 0.0.0.9 - 2026-02-11
+
+* Support a bunch of new Type constructors in `substVarsWith`.
+
 ## 0.0.0.8 - 2024-04-14
 
 * Allow th-abstraction-0.7
diff --git a/src/Language/Haskell/TH/Extras.hs b/src/Language/Haskell/TH/Extras.hs
--- a/src/Language/Haskell/TH/Extras.hs
+++ b/src/Language/Haskell/TH/Extras.hs
@@ -1,4 +1,7 @@
 {-# LANGUAGE CPP, TemplateHaskell #-}
+
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
+
 module Language.Haskell.TH.Extras where
 
 import Control.Monad
@@ -7,7 +10,9 @@
 import Data.Set (Set)
 import qualified Data.Set as Set
 import Language.Haskell.TH
+#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ < 914
 import Language.Haskell.TH.Syntax
+#endif
 import Language.Haskell.TH.Datatype.TyVarBndr
 
 intIs64 :: Bool
@@ -179,13 +184,9 @@
       -- Several of the following cases could all be covered by an "x -> x" case, but
       -- I'd rather know if new cases need to be handled specially in future versions
       -- of Template Haskell.
-#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 710
-      ForallT bndrs cxt t ->
+      ForallT bndrs cxt1 t ->
         let bs' = Set.union bs (Set.fromList (map tvName bndrs))
-        in ForallT bndrs (map (subst bs') cxt) (subst bs' t)
-#else
-      ForallT {} -> error "substVarsWith: ForallT substitutions have not been implemented for GHCs prior to 7.10"
-#endif
+        in ForallT bndrs (map (subst bs') cxt1) (subst bs' t)
       AppT f x -> AppT (subst bs f) (subst bs x)
       SigT t k -> SigT (subst bs t) k
       VarT v -> if Set.member v bs
@@ -195,6 +196,7 @@
       TupleT k -> TupleT k
       ArrowT -> ArrowT
       ListT -> ListT
+      UnboxedTupleT k -> UnboxedTupleT k
 #if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 800
       InfixT t1 x t2 -> InfixT (subst bs t1) x (subst bs t2)
       ParensT t -> ParensT (subst bs t)
@@ -216,9 +218,21 @@
       PromotedTupleT k -> PromotedTupleT k
       StarT -> StarT
 #endif
-#if defined (__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ > 700
-      UnboxedTupleT k -> UnboxedTupleT k
+#if defined (__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 904
+      PromotedInfixT t1 x t2 -> PromotedInfixT (subst bs t1) x (subst bs t2)
+      PromotedUInfixT t1 x t2 -> PromotedUInfixT (subst bs t1) x (subst bs t2)
 #endif
+#if defined (__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 900
+      MulArrowT -> MulArrowT
+#endif
+#if defined (__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 900
+      ForallVisT xs t -> ForallVisT xs (subst bs t)
+#endif
+#if defined (__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 808
+      ImplicitParamT s t -> ImplicitParamT s (subst bs t)
+      AppKindT f x -> AppKindT (subst bs f) (subst bs x)
+#endif
+
     findVar v (tv:_) (AppT _ (VarT v')) | v == v' = tv
     findVar v (_:tvs) (AppT t (VarT _)) = findVar v tvs t
     findVar v _ _ = error $ "substVarsWith: couldn't look up variable substitution for " ++ show v
@@ -227,12 +241,7 @@
 -- | Determine the arity of a kind.
 -- Starting in template-haskell 2.8.0.0, 'Kind' and 'Type' became synonymous.
 kindArity :: Kind -> Int
-#if defined (__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ < 706
 kindArity k = case k of
-  StarK -> 0
-  ArrowK _ k2 -> 1 + kindArity k2
-#else
-kindArity k = case k of
   ForallT _ _ t -> kindArity t
   AppT (AppT ArrowT _) t -> 1 + kindArity t
   SigT t _ -> kindArity t
@@ -240,7 +249,6 @@
   ParensT t -> kindArity t
 #endif
   _ -> 0
-#endif
 
 -- | Given the name of a type constructor, determine its full arity
 tyConArity :: Name -> Q Int
@@ -260,26 +268,16 @@
 tyConArity' n = do
   r <- reify n
   return $ case r of
-#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 800
     TyConI (DataD _ _ ts mk _ _) -> (ts, fromMaybe 0 (fmap kindArity mk))
     TyConI (NewtypeD _ _ ts mk _ _) -> (ts, fromMaybe 0 (fmap kindArity mk))
-#else
-    TyConI (DataD _ _ ts _ _) -> (ts, 0)
-    TyConI (NewtypeD _ _ ts _ _) -> (ts, 0)
-#endif
     _ -> error $ "tyConArity': Supplied name reified to something other than a data declaration: " ++ show n
 
 -- | Determine the constructors bound by a data or newtype declaration. Errors out if supplied with another
 -- sort of declaration.
 decCons :: Dec -> [Con]
 decCons d = case d of
-#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 800
   DataD _ _ _ _ cs _ -> cs
   NewtypeD _ _ _ _ c _ -> [c]
-#else
-  DataD _ _ _ cs _ -> cs
-  NewtypeD _ _ _ c _ -> [c]
-#endif
   _ -> error "decCons: Declaration found was not a data or newtype declaration."
 
 -- | Determine the arity of a data constructor.
@@ -289,7 +287,5 @@
   RecC _ ts -> length ts
   InfixC _ _ _ -> 2
   ForallC _ _ c' -> conArity c'
-#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 800
   GadtC _ ts _ -> length ts
   RecGadtC _ ts _ -> length ts
-#endif
diff --git a/th-extras.cabal b/th-extras.cabal
--- a/th-extras.cabal
+++ b/th-extras.cabal
@@ -1,5 +1,5 @@
 name:                   th-extras
-version:                0.0.0.8
+version:                0.0.0.9
 stability:              experimental
 
 cabal-version:          >= 1.10
@@ -19,8 +19,11 @@
                         providing high-level operations and making sure they work on as many
                         versions of Template Haskell as I can.
 tested-with:
-                        GHC == 9.8.2
-                        GHC == 9.6.4
+                        GHC == 9.14.1
+                        GHC == 9.12.2
+                        GHC == 9.10.3
+                        GHC == 9.8.4
+                        GHC == 9.6.7
                         GHC == 9.4.8
                         GHC == 9.2.8
                         GHC == 9.0.2
@@ -40,10 +43,11 @@
 
 Library
   hs-source-dirs:       src
+  ghc-options:          -Wall
   exposed-modules:      Language.Haskell.TH.Extras
   build-depends:        base >= 4.9 && < 5
-                      , containers
-                      , template-haskell < 2.23
+                      , containers < 0.9
+                      , template-haskell < 2.25
                       , th-abstraction >= 0.4 && < 0.8
-                      , syb
+                      , syb < 0.8
   default-language:     Haskell2010