CommonJS exporting a hash of functions not working

I have a few js files that group together some utility functions that are structured like this example:

``` js
/** @module calculator */

/**
* Adds two numbers
* @param {number} a - The first number
* @param {number} b - The second number
* @returns {number} - The addition result
*/
function add(a, b) {
return a + b;
}

module.exports = {
add,
};
```

Running the documentaionjs 8.1.2 cli on this gives me an empty module calculator and the function add. Since I export add as part of the module I would expect it to be documented as part of it.