See the issue and the test case with original fix in https://github.com/facebook/react/pull/14802.

We'll need to fix it properly, see https://github.com/facebook/react/pull/14802#issuecomment-463277621.
render() {
        return (
          <div>
            <span className="child1" />
            <span className="child2" />
          </div>
        );
      }