How to stub a required function in Sinon?

I am trying to stub a required function in my file. For example:

fileA.js

function doSomething() {
  return 5;
}

modules.export = { doSomething }

fileB.js

const { doSomething } = require('./fileA');

function doAnotherThing() {
  let anotherThing = 10;
  return anotherThing + doSomething();
}

modules.export = { doAnotherThing }

And in my test file: fileBTest.js

const fileA = require('./fileA');
const fileB = require('./fileB');

describe('Test File B', function(){
  it('Example of failing stub', function() {
    const fileAStub = sinon.stub(fileA, 'doSomething');
    fileAStub.returns(15);

    expect(fileB.doAnotherThing()).to.equal(25);
  })
})

However, my fileAStub is not working because in fileB.js, it is required as a function and not the entire fileA being required.

If I change the way I require fileA in fileB.js to the following, my stub will work.

updatedFileB.js

const fileA = require('./fileA');

function doAnotherThing() {
  let anotherThing = 10;
  return anotherThing + fileA.doSomething();
}

Question: How can I stub { doSomething } instead of changing the way I do require in fileB?