1 files changed, 17 insertions, 0 deletions
diff --git a/testsuite/tests/deriving/should_compile/T23329_M.hs b/testsuite/tests/deriving/should_compile/T23329_M.hs
new file mode 100644
index 0000000000..a451a2b828
--- /dev/null
+++ b/testsuite/tests/deriving/should_compile/T23329_M.hs
@@ -0,0 +1,17 @@
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE UndecidableInstances #-}
+module T23329_M where
+
+import Data.Kind (Type)
+import Data.Proxy (Proxy)
+
+class MyClass (f :: k -> Type) where
+  type MyTypeFamily f (i :: k) :: Type
+  myMethod :: MyTypeFamily f i -> Proxy f -> Proxy i -> ()
+
+instance MyClass Maybe where
+  type MyTypeFamily Maybe i = ()
+  myMethod = undefined
+
+newtype MyMaybe a = MyMaybe (Maybe a)
+  deriving MyClass