Getting issue while creating to create ToJSON instance using aeson template in `aeson-1.4.7.1`

getting error while trying to create ToJSON instance for type Exp. using aeson 1.4.7.1

```
import qualified Data.Aeson.TH as AesonTH
import Data.Functor.Identity as DF

data ExpT f =
ExpT
{
name :: f Text,
age :: f Int
} deriving (Generic)

type Exp = ExpT DF.Identity

deriving instance Eq Exp

$(AesonTH.deriveToJSON AesonTH.defaultOptions ''ExpT)
```

getting error
``` normalizeDecFor: DataD or NewtypeD required ```