Error while compiling servant-client-0.20.2

[saurabhnanda]

I'm on ghc-8.10.7 and got the following error (downgrading to servant-client-0.20 solved the issue, for now, at least):

servant-client > /tmp/stack-f7661c0549ae3b6c/servant-client-0.20.2/src/Servant/Client/Internal/HttpClient.hs:137:60: error:
servant-client >     * No instance for (Generic
servant-client >                          (ReaderT ClientEnv (ExceptT ClientError IO) a))
servant-client >         arising from the 'deriving' clause of a data type declaration
servant-client >       Possible fix:
servant-client >         use a standalone 'deriving instance' declaration,
servant-client >           so you can specify the instance context yourself
servant-client >     * When deriving the instance for (Generic (ClientM a))
servant-client >     |
servant-client > 137 |   deriving newtype ( Functor, Applicative, Monad, MonadIO, Generic
servant-client >     |                                                            ^^^^^^^
servant-client >