diff -r 000000000000 -r 6474c204b198 toolkit/mozapps/extensions/test/xpcshell/test_bad_json.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_bad_json.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,54 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+// Tests that we rebuild the database correctly if it contains
+// JSON data that parses correctly but doesn't contain required fields
+
+var addon1 = {
+  id: "addon1@tests.mozilla.org",
+  version: "2.0",
+  name: "Test 1",
+  targetApplications: [{
+    id: "xpcshell@tests.mozilla.org",
+    minVersion: "1",
+    maxVersion: "1"
+  }]
+};
+
+const profileDir = gProfD.clone();
+profileDir.append("extensions");
+
+function run_test() {
+  do_test_pending("Bad JSON");
+
+  createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1", "1.9.2");
+
+  // This addon will be auto-installed at startup
+  writeInstallRDFForExtension(addon1, profileDir);
+
+  startupManager();
+
+  shutdownManager();
+
+  // First startup/shutdown finished
+  // Replace the JSON store with something bogus
+  saveJSON({not: "what we expect to find"}, gExtensionsJSON);
+
+  startupManager(false);
+  // Retrieve an addon to force the database to rebuild
+  AddonManager.getAddonsByIDs([addon1.id], callback_soon(after_db_rebuild));
+}
+
+function after_db_rebuild([a1]) {
+  do_check_eq(a1.id, addon1.id);
+
+  shutdownManager();
+
+  // Make sure our JSON database has schemaVersion and our installed extension
+  let data = loadJSON(gExtensionsJSON);
+  do_check_true("schemaVersion" in data);
+  do_check_eq(data.addons[0].id, addon1.id);
+
+  do_test_finished("Bad JSON");
+}