No code reload when using mocha --watch and 0.18.0

I'm using Reify with Mocha 5.2.0 to auto-reload as I make changes to my project like so:

```bash
node_modules/.bin/mocha -G --recursive --watch --reporter min --require reify
```

I see expected behavior with Reify 0.17.3. When a module under test changes, Mocha re-runs and produces output that reflects the changes I made to code under test.

I see something different with Reify 0.18.0. When code under test changes, Mocha re-runs but the changes made to the file are not reflected in Mocha's output. A test that starts failing stays failing, regardless of what changes are made to the file.

I see the same behavior whether I clear the `.reify-cache` directory between a 0.17.3->0.18.0 upgrade or not.

Ideas?