Surprising behavior with Generic deriving

I am building out a Servant api containing the following type:

```
data NotVerified = NotVerified
deriving stock (Generic)
deriving anyclass (ToJSON, FromJSON)

data NotVerifiedResponse = NotVerifiedResponse { errorCode :: NotVerified }
deriving stock (Generic)
deriving anyclass (ToJSON, FromJSON)
```

Strangely, if I JSON encode the NotVerifiedResponse I get

```
encode $ NotVerifiedResponse { errorCode = NotVerified }
"{\"errorCode\":[]}"
```

I'd expect to see

```
"{\"errorCode\":\"NotVerified\"}"
```

I am using GHC 9.10.3 and aeson 2.2.3.0