diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,9 @@
+# 0.1.2.0
+
+- Fail correctly, with appropriate error message, when deriving Matchable
+  and Bimatchable fails due to the datatype having zero (Matchable) or
+  less than two (Bimatchable) parameters.
+
 # 0.1.1.1
 
 - Use "th-abstraction" >= 0.4 to cover changes in forthcoming
diff --git a/matchable-th.cabal b/matchable-th.cabal
--- a/matchable-th.cabal
+++ b/matchable-th.cabal
@@ -1,5 +1,5 @@
 name:                matchable-th
-version:             0.1.1.1
+version:             0.1.2.0
 synopsis:            Generates Matchable instances using TemplateHaskell
 description:         This package provides TemplateHaskell function to generate
                      instances of @Matchable@ and @Bimatchable@ type classes,
@@ -23,7 +23,7 @@
   exposed-modules:      Data.Matchable.TH
   build-depends:        base               >= 4.10       && <5,
                         matchable          >= 0.1.2,
-                        template-haskell   >= 2.4 && < 2.17,
+                        template-haskell   >= 2.4 && < 2.18,
                         th-abstraction     >= 0.4.0.0
   ghc-options:          -Wall
   default-language:     Haskell2010
@@ -34,3 +34,4 @@
   main-is:             th.hs
   build-depends:       base, containers, matchable, matchable-th
   default-language:    Haskell2010
+
diff --git a/src/Data/Matchable/TH.hs b/src/Data/Matchable/TH.hs
--- a/src/Data/Matchable/TH.hs
+++ b/src/Data/Matchable/TH.hs
@@ -46,13 +46,19 @@
 makeZipMatchWith :: Name -> ExpQ
 makeZipMatchWith name = makeZipMatchWith' name >>= snd
 
+viewLast :: [a] -> Maybe ([a], a)
+viewLast as = case reverse as of
+  [] -> Nothing
+  a:rest -> Just (reverse rest, a)
+
 makeZipMatchWith' :: Name -> Q ((Q Cxt, Type), ExpQ)
 makeZipMatchWith' name = do
   info <- reifyDatatype name
-  let DatatypeInfo { datatypeVars = dtVars , datatypeCons = cons } = info
-      tyA : rest' = reverse (VarT . tvName <$> dtVars)
-      dtFunctor = foldr (flip AppT) (ConT name) rest'
-
+  let DatatypeInfo { datatypeVars = dtVarsNames , datatypeCons = cons } = info
+  (dtFunctor, tyA) <- case viewLast (VarT . tvName <$> dtVarsNames) of
+    Nothing -> fail $ "Not a type constructor:" ++ show name
+    Just (rest, tyA) -> return (foldl AppT (ConT name) rest, tyA)
+  
   f <- newName "f"
 
   let mkMatchClause (ConstructorInfo ctrName _ _ fields _ _) =
@@ -218,12 +224,18 @@
 makeBizipMatchWith :: Name -> ExpQ
 makeBizipMatchWith name = makeBizipMatchWith' name >>= snd
 
+viewLastTwo :: [a] -> Maybe ([a],a,a)
+viewLastTwo as = case reverse as of
+  b:a:rest -> Just (reverse rest, a, b)
+  _ -> Nothing
+
 makeBizipMatchWith' :: Name -> Q ((Q Cxt, Type), ExpQ)
 makeBizipMatchWith' name = do
   info <- reifyDatatype name
   let DatatypeInfo { datatypeVars = dtVars , datatypeCons = cons } = info
-      tyB : tyA : rest' = reverse (VarT . tvName <$> dtVars)
-      dtFunctor = foldr (flip AppT) (ConT name) rest'
+  (dtFunctor, tyA, tyB) <- case viewLastTwo (VarT . tvName <$> dtVars) of
+      Nothing -> fail $ "Not a datatype with at least 2 parameters: " ++ show name
+      Just (rest, tyA, tyB) -> return (foldl AppT (ConT name) rest, tyA, tyB)
 
   f <- newName "f"
   g <- newName "g"
diff --git a/test/th.hs b/test/th.hs
--- a/test/th.hs
+++ b/test/th.hs
@@ -1,6 +1,7 @@
 {-# LANGUAGE DeriveTraversable #-}
 {-# LANGUAGE TemplateHaskell #-}
 {-# LANGUAGE UndecidableInstances #-}
+{-# LANGUAGE FlexibleContexts #-}
 module Main(main) where
 
 import           Data.Functor.Classes