diff --git a/common/content/javascript.js b/common/content/javascript.js
index 0bcb2f5d..4eadce71 100644
--- a/common/content/javascript.js
+++ b/common/content/javascript.js
@@ -592,7 +592,7 @@ const JavaScript = Module("javascript", {
      * A list of properties of the global object which are not
      * enumerable by any standard method.
      */
-    globalNames: [
+    globalNames: array.uniq([
         "Array", "ArrayBuffer", "AttributeName", "Boolean", "Date", "Error",
         "EvalError", "Function", "Infinity", "Iterator", "JSON", "Math", "NaN",
         "Namespace", "Number", "Object", "QName", "RangeError",
@@ -603,9 +603,9 @@ const JavaScript = Module("javascript", {
         "isFinite", "isNaN", "isXMLName", "parseFloat", "parseInt", "undefined",
         "uneval", "Int8Array", "Uint8Array", "Int16Array", "Uint16Array",
         "Int32Array", "Uint32Array", "Float32Array", "Float64Array", "Proxy",
-    ].concat(
-        [k.substr(6) for (k in keys(Ci)) if (/^nsIDOM/.test(k))]
-            .filter(function (k) k in window)),
+    ].concat([k.substr(6) for (k in keys(Ci)) if (/^nsIDOM/.test(k))])
+     .concat([k.substr(3) for (k in keys(Ci)) if (/^nsI/.test(k))])
+     .filter(function (k) k in window)),
 
     /**
      * Installs argument string completers for a set of functions.