TypeError: Property 'be' of object #<Assertion> is not a function

I feel like this has to be user error but here's what I'm seeing. Using expect.js 0.1.2 with chai and mocha.

The following produces an error:
`expect(1).to.be(1);`
TypeError: Property 'be' of object # is not a function

But if I do something like this it works:
`expect(1).to.eql(1);`