diff --git a/services/sync/modules/engines/addons.js b/services/sync/modules/engines/addons.js
index 5ad13b9213b..1221ed91cec 100644
--- a/services/sync/modules/engines/addons.js
+++ b/services/sync/modules/engines/addons.js
@@ -275,6 +275,8 @@ AddonsStore.prototype = {
   // Define the add-on types (.type) that we support.
   _syncableTypes: ["extension", "theme"],
 
+  _extensionsPrefs: new Preferences("extensions."),
+
   get reconciler() {
     return this.engine._reconciler;
   },
@@ -539,7 +541,8 @@ AddonsStore.prototype = {
     //   2) Installed in the current profile
     //   3) Not installed by a foreign entity (i.e. installed by the app)
     //      since they act like global extensions.
-    //   4) Are installed from AMO
+    //   4) Is not a hotfix.
+    //   5) Are installed from AMO
 
     // We could represent the test as a complex boolean expression. We go the
     // verbose route so the failure reason is logged.
@@ -568,6 +571,12 @@ AddonsStore.prototype = {
       return false;
     }
 
+    // Ignore hotfix extensions (bug 741670). The pref may not be defined.
+    if (this._extensionsPrefs.get("hotfix.id", null) == addon.id) {
+      this._log.debug(addon.id + " not syncable: is a hotfix.");
+      return false;
+    }
+
     // We provide a back door to skip the repository checking of an add-on.
     // This is utilized by the tests to make testing easier. Users could enable
     // this, but it would sacrifice security.
diff --git a/services/sync/tests/unit/test_addons_store.js b/services/sync/tests/unit/test_addons_store.js
index 8ff4dad9f7a..2fbccf19d89 100644
--- a/services/sync/tests/unit/test_addons_store.js
+++ b/services/sync/tests/unit/test_addons_store.js
@@ -367,6 +367,48 @@ add_test(function test_addon_syncability() {
   run_next_test();
 });
 
+add_test(function test_ignore_hotfixes() {
+  _("Ensure that hotfix extensions are ignored.");
+
+  Svc.Prefs.set("addons.ignoreRepositoryChecking", true);
+
+  // A hotfix extension is one that has the id the same as the
+  // extensions.hotfix.id pref.
+  let prefs = new Preferences("extensions.");
+
+  let addon = installAddon("test_bootstrap1_1");
+  do_check_true(store.isAddonSyncable(addon));
+
+  let dummy = {};
+  const KEYS = ["id", "syncGUID", "type", "scope", "foreignInstall"];
+  for each (let k in KEYS) {
+    dummy[k] = addon[k];
+  }
+
+  // Basic sanity check.
+  do_check_true(store.isAddonSyncable(dummy));
+
+  prefs.set("hotfix.id", dummy.id);
+  do_check_false(store.isAddonSyncable(dummy));
+
+  // Verify that int values don't throw off checking.
+  let prefSvc = Cc["@mozilla.org/preferences-service;1"]
+                .getService(Ci.nsIPrefService)
+                .getBranch("extensions.");
+  // Need to delete pref before changing type.
+  prefSvc.deleteBranch("hotfix.id");
+  prefSvc.setIntPref("hotfix.id", 0xdeadbeef);
+
+  do_check_true(store.isAddonSyncable(dummy));
+
+  uninstallAddon(addon);
+
+  Svc.Prefs.reset("addons.ignoreRepositoryChecking");
+  prefs.reset("hotfix.id");
+
+  run_next_test();
+});
+
 add_test(function test_ignore_untrusted_source_uris() {
   _("Ensures that source URIs from insecure schemes are rejected.");