How to use RpcGroup prefix and merge correctly?

export class UserRpcGroup extends RpcGroup.make(
  Rpc.fromTaggedRequest(UserAuthenticatedQuery),
  Rpc.fromTaggedRequest(UserDetailsUpdateMutation),
).prefix('user.') {}

export class DeviceBrandRpcGroup extends RpcGroup.make(
  Rpc.fromTaggedRequest(DeviceBrandCreateMutation),
).prefix('deviceBrand.') {}

export class AppRpcGroup extends RpcGroup.make().merge(
  UserRpcGroup,
  DeviceBrandRpcGroup,
) {}

'extends' clause of exported class 'UserRpcGroup' has or is using private name 'RefineSchemaId'.ts(4020)
'extends' clause of exported class 'AppRpcGroup' has or is using private name 'RefineSchemaId'.ts(4020)