`html` behaves unexpectedly when there is no indent

I am trying no nest codeBlock (or html), but I am unable to do this for the root level indentation:

```js
import { codeBlock } from 'common-tags';

const bc = () => codeBlock`
B
C
`;

const a = () => codeBlock`
A
${bc()}
  ${bc()}
`;

console.log(a());
```

gives me
```
A
B C
  B
  C
```

but I would expect it to be:
```
A
B
C
  B
  C
```