webstorm + typescript "unresolved variable" after adding reference path

I'm using the latest WebStorm EAP 7 130.958.

I have had this buggy behavior since version 6 came out with Typescript support. The problem in the below example code applies "unresolved variable" to BaseClass in the ExtendedClass.ts the moment I add ...

///<reference path="./Interfaces.ts"/>

If I remove reference path the error goes away. This happens any time I extend from a class imported from a node module ONLY when a reference path exists. How did this make it all the way through 6 to 7?

Interfaces.ts

interface IBaseClass {
    str:string;
}

BaseClass.ts

///<reference path="./Interfaces.ts"/>
export class BaseClass implements IBaseClass{
    constructor(public str:string){
        return str+str;
    }
}

ExtendedClass.ts

///<reference path="./Interfaces.ts"/>
import baseClassModule = module("./BaseClass");

class ExtendedClass extends baseClassModule.BaseClass{
    constructor(public str:string){
        super(str);
    }
}

var extendedClass:ExtendedClass = new ExtendedClass("yo");

console.log(extendedClass);