Boolean fields (published, sticky, promoted, fieldAPI) always saved as true regardless of what value is passed

To reproduce:

• Install D7 + backbone + backbone_example
• Create an article with published, promoted, and sticky unchecked
• Open browser's JS console and execute following:
  

  var m = new Drupal.Backbone.Models.Node;
  m.set({nid: 1});
  m.fetch();
  m.save({title: 'new title'});

• Surf to /node/1/edit to confirm that all three boolean fields (published, promoted, sticky are now checked)

Examining the PUT request, the sent values are correct, so it appears to be something on the Drupal/PHP side. Bellow is the JSON sent in the request

• {
     "node":{
        "nid":"1",
        "vid":"1",
        "uid":"1",
        "title":"new title",
        "log":"",
        "status":"0",
        "comment":"1",
        "promote":"0",
        "sticky":"0",
        "type":"article",
        "language":"und",
        "created":"1336140139",
        "changed":"1336141992",
        "tnid":"0",
        "translate":"0",
        "revision_timestamp":"1336141992",
        "revision_uid":"1",
        "body":{
           "und":[
              {
                 "value":"Super duper!!!",
                 "summary":"",
                 "format":"filtered_html",
                 "safe_value":"<p>Super duper!!!</p>\n",
                 "safe_summary":""
              }
           ]
        },
        "field_tags":[
  
        ],
        "field_image":[
  
        ],
        "rdf_mapping":{
           "field_image":{
              "predicates":[
                 "og:image",
                 "rdfs:seeAlso"
              ],
              "type":"rel"
           },
           "field_tags":{
              "predicates":[
                 "dc:subject"
              ],
              "type":"rel"
           },
           "rdftype":[
              "sioc:Item",
              "foaf:Document"
           ],
           "title":{
              "predicates":[
                 "dc:title"
              ]
           },
           "created":{
              "predicates":[
                 "dc:date",
                 "dc:created"
              ],
              "datatype":"xsd:dateTime",
              "callback":"date_iso8601"
           },
           "changed":{
              "predicates":[
                 "dc:modified"
              ],
              "datatype":"xsd:dateTime",
              "callback":"date_iso8601"
           },
           "body":{
              "predicates":[
                 "content:encoded"
              ]
           },
           "uid":{
              "predicates":[
                 "sioc:has_creator"
              ],
              "type":"rel"
           },
           "name":{
              "predicates":[
                 "foaf:name"
              ]
           },
           "comment_count":{
              "predicates":[
                 "sioc:num_replies"
              ],
              "datatype":"xsd:integer"
           },
           "last_activity":{
              "predicates":[
                 "sioc:last_activity_date"
              ],
              "datatype":"xsd:dateTime",
              "callback":"date_iso8601"
           }
        },
        "cid":"0",
        "last_comment_timestamp":"1336140139",
        "last_comment_name":null,
        "last_comment_uid":"1",
        "comment_count":"0",
        "name":"root",
        "picture":"0",
        "data":"b:0;",
        "path":"http://t.dev/node/1"
     }
  }