Created Unassigned: Error reading package.json [1594]

I'm getting the following error when installing packages from npm:

> Microsoft.NodejsTools.Npm.PackageJsonException: Error reading package.json at 'xxx\node_modules\express-session\node_modules\utils-merge\package.json': Unable to read package.json. Please ensure the file is valid JSON.

I've looked at the mentioned package.json and put it trough various validators and all returned saying the json is valid.

See attachments for the complete error and see the package.json (same as installed) here https://github.com/jaredhanson/utils-merge/blob/master/package.json.