Error: Cannot read properties of undefined (reading 'indexOf')

[kumailn]

I have a simple app setup as follows:

import { importQL } from 'https://deno.land/x/importql/mod.ts';
import { Application } from 'https://deno.land/x/oak@v12.1.0/mod.ts';
import { Router } from 'https://deno.land/x/oak@v6.0.1/mod.ts';
import { ObsidianRouter } from 'https://deno.land/x/obsidian/mod.ts';
import { resolvers } from './resolvers.ts';
const types = importQL('schema.graphql');

const PORT = 1111;
const app = new Application();
const router = new Router();

interface ObsRouter extends Router {
  obsidianSchema?: any;
}

const GraphQLRouter = await ObsidianRouter<ObsRouter>({
  Router,
  typeDefs: types,
  resolvers: resolvers,
  useCache: true,
  usePlayground: true,
  context: (request) => {
    return {
      ...request,
      secret: request?.request?.headers?.get('apiKey'),
      ip: request?.request?.headers?.get('x-forwarded-for') || request?.request?.ip,
      referer: request?.request?.headers?.get('referer'),
    };
  },
});

app.use(router.routes(), router.allowedMethods());
app.use(GraphQLRouter.routes(), GraphQLRouter.allowedMethods());

await app.listen({
  port: PORT,
});

When I run a simple query in my graphql playground such as

query getBook {
  book(id:"1") {
    id
  }
}

I get an error Cannot read properties of undefined (reading 'indexOf'). If I set useCache: false then this error does not occur. Redis is running on the default port. Is there something wrong with my setup or is this a bug?