WebStorm not recognising Mocha describe() and it()

I admit that I'm being pedantic here. I have a Mocha test in WebStorm and WebStorm is complaining about describe() and it() not being a function type.

I have the mocha-definatelyTyped library downloaded, and added to the tests folder.

Running Mocha is fine. Why is WebStorm not resolving the describe and it methods?