diff --git a/browser/base/content/test/Makefile.in b/browser/base/content/test/Makefile.in
index 94e408d2d82..0d9b59df69c 100644
--- a/browser/base/content/test/Makefile.in
+++ b/browser/base/content/test/Makefile.in
@@ -146,6 +146,7 @@ _BROWSER_FILES = \
                  browser_ctrlTab.js \
                  browser_discovery.js \
                  browser_drag.js \
+                 browser_duplicateIDs.js \
                  browser_gestureSupport.js \
                  browser_getshortcutoruri.js \
                  browser_hide_removing.js \
diff --git a/browser/base/content/test/browser_duplicateIDs.js b/browser/base/content/test/browser_duplicateIDs.js
new file mode 100644
index 00000000000..38fc17820e5
--- /dev/null
+++ b/browser/base/content/test/browser_duplicateIDs.js
@@ -0,0 +1,8 @@
+function test() {
+  var ids = {};
+  Array.forEach(document.querySelectorAll("[id]"), function (node) {
+    var id = node.id;
+    ok(!(id in ids), id + " should be unique");
+    ids[id] = null;
+  });
+}