enzyme: .instance() doesn't return dom node(null instead)

When I try to find .value of an input DOM node .instance() returns null. In enzyme@2* it was very ok with .get(0).

What was in enzyme 2* and worked:

const wrapper = mount(<MyComp>); // input somewhere within tree
const inputNode = wrapper.find('input').get(0);
expect(inputNode.value).toBe('0');

In enzyme 3 this doesn’t work. I’ve tried to do this (which should work by documentation):

const wrapper = mount(<MyComp>);
const inputNode = wrapper.find('input').instance();  // <------ returns NULL
expect(inputNode.value).toBe('0');

Is this a bug or I missed something?

P.S. React is 15.1.0 with enzyme-adapter-react-15.4