Ember 1.10.0 throws "Uncaught Error: Bound attributes are not yet supported in Ember.js"

I just changed this:

  <div {{bind-attr class=":step category.isCurrent:active category.isBeforeCurrent:visited"}}>

to this:

<div class="step {{category.isCurrent:active}} {{category.isBeforeCurrent:visited}}">

and now get:

Uncaught Error: Bound attributes are not yet supported in Ember.js

bower:

{
  "name": "proj",
  "dependencies": {
    "jquery": "^1.11.1",
    "ember": "1.10.0",
    "ember-data": "^1.0.0-beta.14.1",
    "ember-resolver": "~0.1.11",
    "loader.js": "ember-cli/loader.js#1.0.1",
    "ember-cli-shims": "ember-cli/ember-cli-shims#0.0.3",
    "ember-cli-test-loader": "rwjblue/ember-cli-test-loader#0.0.4",
    "ember-load-initializers": "ember-cli/ember-load-initializers#0.0.2",
    "ember-qunit": "0.1.8",
    "ember-qunit-notifications": "0.0.4",
    "qunit": "~1.15.0"
  }
}