Weird data type when extending context in fetch adapter

// context.ts
import { FetchCreateContextFnOptions } from "@trpc/server/adapters/fetch";

export const createContext = async ({
  req,
  resHeaders,
  env,
}: FetchCreateContextFnOptions & { env: Env }) => {
  return { req, resHeaders, env };
};

export type Context = Awaited<ReturnType<typeof createContext>>;

// workers index
import {
  FetchCreateContextFnOptions,
  fetchRequestHandler,
} from "@trpc/server/adapters/fetch";
import { createContext } from "./context";
import { appRouter } from "./router";

export default {
  fetch(request, env) {
    const url = new URL(request.url);

    if (url.pathname.startsWith("/api")) {
      return fetchRequestHandler({
        endpoint: "/api",
        req: request,
        router: appRouter,
        // add env to the context along with defaults
        createContext: (opts: FetchCreateContextFnOptions) =>
          createContext({ ...opts, env }),
      });
    }

    return env.ASSETS.fetch(request);
  },
} satisfies ExportedHandler<Env>;

const query = useQuery(trpc.kvQuery.queryOptions())
query.data
//      ^ (() => never) | undefined