ember-inspector: 'Cannot add property toString, object is not extensible'

Hey all,

Our team has recently ran into this Ember Inspector related error with the latest 2.1.0 release that went out a few hours ago. The quickest way to see this is to inspect any Ember model in the data store view. Has anyone else experienced this?

Ember Inspector has errored.
This is likely a bug in the inspector itself.
You can report bugs at https://github.com/emberjs/ember-inspector.
Error message: Cannot add property toString, object is not extensible
Stack trace: TypeError: Cannot add property toString, object is not extensible
    at Mixin.classToString [as toString] (http://localhost:5000/assets/vendor.js:58602:21)
    at mixins.forEach.mixin (<anonymous>:3029:24)
    at Array.forEach (<anonymous>)
    at Class.mixinsForObject (<anonymous>:3026:14)
    at Class.sendObject (<anonymous>:2942:26)
    at Class.inspectModel (<anonymous>:856:37)
    at Object.sendEvent (http://localhost:5000/assets/vendor.js:39028:18)
    at Class.trigger (http://localhost:5000/assets/vendor.js:55337:25)
    at wrap (<anonymous>:3438:14)
    at Class.<anonymous> (<anonymous>:3468:18)

The last part of that stack traces stops here:

function classToString() {
    if (!searchDisabled && !this[_emberMetalMixin.NAME_KEY]) {
      processAllNamespaces();
    }

    var ret = undefined;

    if (this[_emberMetalMixin.NAME_KEY]) {
      ret = this[_emberMetalMixin.NAME_KEY];
    } else if (this._toString) {
      ret = this._toString;
    } else {
      var str = superClassString(this);
      if (str) {
        ret = '(subclass of ' + str + ')';
      } else {
        ret = '(unknown mixin)';
      }
      this.toString = makeToString(ret);
    }

    return ret;
  }

at ‘this.toString = makeToString(ret);’ (ret being ‘(unknown mixin)’)

We’re using the following library versions:

Ember Inspector | 2.1.0 Ember | 2.8.1 Ember Data | 2.8.1 jQuery | 2.1.4

Thanks in advance!