Incompatibility with react-md

I was testing @mlaursen's [react-md](https://github.com/mlaursen/react-md) with Preact, but can't get it to run. The Chrome console shows this error:

![image](https://user-images.githubusercontent.com/33569/44614789-bc177680-a7df-11e8-9fcc-a99a07b67dec.png)

Repro repo at https://github.com/dandv/preact-react-md