diff --git a/mozilla/js/src/xpconnect/src/xpccomponents.cpp b/mozilla/js/src/xpconnect/src/xpccomponents.cpp
index 0f950dd96d8..0ae14edab4c 100644
--- a/mozilla/js/src/xpconnect/src/xpccomponents.cpp
+++ b/mozilla/js/src/xpconnect/src/xpccomponents.cpp
@@ -1093,6 +1093,38 @@ nsXPCComponents::Create(JSContext *cx, JSObject *obj,
         "this.Exception.toString = function() {\n"
         "  return '\\nfunction Exception() {\\n    [JavaScript code]\\n}\\n';\n"
         "};\n"
+        "\n"
+        "this.Constructor = function(progid, iid, fname) {\n"
+        "  if(!arguments.length)\n"
+        "    throw 'Components.Constructor requires at least one argument';\n"
+        "  if(!Components.classes[progid])\n"
+        "    throw ''+progid+' is not a registered progid';\n"
+        "  if(iid && !Components.interfaces[iid])\n"
+        "    throw ''+iid+' is not a valid interface id';\n"
+        "  switch(arguments.length) {\n"
+        "  case 1:\n"
+        "    return function() {\n"
+        "      return Components.classes[progid].createInstance();\n"
+        "    }\n"
+        "  case 2:\n"
+        "    return function() {\n"
+        "      return Components.classes[progid].createInstance(Components.interfaces[iid]);\n"
+        "    }\n"
+        "  default:\n"
+        "    return function() {\n"
+        "      var o = Components.classes[progid].createInstance(Components.interfaces[iid]);\n"
+        "      var f = o[fname];\n"
+        "      if(!f)\n"
+        "        throw ''+fname+' is not a method of '+iid;\n"
+        "      f.apply(o,arguments);\n"
+        "      return o;\n"
+        "    }\n"
+        "  }\n"
+        "}\n"
+        "this.Constructor.toString = function() {\n"
+        "  return '\\nfunction Constructor() {\\n    [JavaScript code]\\n}\\n';\n"
+        "};\n"
+        "\n"
         ;
 
     jsval ignored;