diff --git a/common/content/completion.js b/common/content/completion.js
index 179c77a9..a7a08c34 100644
--- a/common/content/completion.js
+++ b/common/content/completion.js
@@ -347,9 +347,15 @@ const CompletionContext = Class("CompletionContext", {
             this.lastActivated = this.top.runCount;
         }
         if (!this.itemCache[this.key]) {
-            let res = this._generate.call(this);
-            if (res != null)
-                this.itemCache[this.key] = res;
+            try {
+                let res = this._generate.call(this);
+                if (res != null)
+                    this.itemCache[this.key] = res;
+            }
+            catch (e) {
+                dactyl.reportError(e);
+                this.message = "Error: " + e;
+            }
         }
         return this.itemCache[this.key];
     },
diff --git a/common/content/dactyl-overlay.js b/common/content/dactyl-overlay.js
index 04f0ddfa..4b661344 100644
--- a/common/content/dactyl-overlay.js
+++ b/common/content/dactyl-overlay.js
@@ -5,7 +5,8 @@
 "use strict";
 
 (function () {
-    const modules = {};
+    const jsmodules = {}
+    const modules = { __proto__: jsmodules };
     const BASE = "chrome://dactyl/content/";
 
     modules.modules = modules;
@@ -27,7 +28,7 @@
             }
         }
         try {
-            Components.utils.import("resource://dactyl/" + script + ".jsm", modules);
+            Components.utils.import("resource://dactyl/" + script + ".jsm", jsmodules);
         }
         catch (e) {
             dump("dactyl: Loading script " + script + ": " + e.result + " " + e + "\n");
diff --git a/common/content/javascript.js b/common/content/javascript.js
index 3626c42c..2a13e356 100644
--- a/common/content/javascript.js
+++ b/common/content/javascript.js
@@ -39,7 +39,8 @@ const JavaScript = Module("javascript", {
             return;
 
         let seen = {};
-        for (let key in properties(obj, !toplevel)) {
+        let globals = values(toplevel && Class.objectGlobal(obj) === obj ? JavaScript.globalNames : []);
+        for (let key in iterAll(globals, properties(obj, !toplevel))) {
             set.add(seen, key);
             yield key;
         }
@@ -587,6 +588,17 @@ const JavaScript = Module("javascript", {
      */
     completers: {},
 
+    /**
+     * A list of properties of the global object which are not
+     * enumerable by any standard method.
+     */
+    globalNames: ["Array", "Boolean", "Date", "Error", "EvalError",
+        "Function", "Infinity", "Math", "NaN", "Number", "Object",
+        "RangeError", "ReferenceError", "RegExp", "String",
+        "SyntaxError", "TypeError", "URIError", "decodeURI",
+        "decodeURIComponent", "encodeURI", "encodeURIComponent", "eval",
+        "isFinite", "isNaN", "parseFloat", "parseInt", "undefined"],
+
     /**
      * Installs argument string completers for a set of functions.
      * The second argument is an array of functions (or null
diff --git a/common/modules/base.jsm b/common/modules/base.jsm
index 413df1a0..68d10ded 100644
--- a/common/modules/base.jsm
+++ b/common/modules/base.jsm
@@ -734,8 +734,9 @@ function Module(name, prototype) {
     defineModule.modules.push(instance);
     return module;
 }
+
 if (Cu.getGlobalForObject)
-    Module.callerGlobal = function (caller) {
+    Class.objectGlobal = function (caller) {
         try {
             return Cu.getGlobalForObject(caller);
         }
@@ -744,7 +745,7 @@ if (Cu.getGlobalForObject)
         }
     };
 else
-    Module.callerGlobal = function (caller) {
+    Class.objectGlobal = function (caller) {
         while (caller.__parent__)
             caller = caller.__parent__;
         return caller;
diff --git a/common/modules/sanitizer.jsm b/common/modules/sanitizer.jsm
index cf0b131d..1dec97b9 100644
--- a/common/modules/sanitizer.jsm
+++ b/common/modules/sanitizer.jsm
@@ -103,7 +103,7 @@ const Sanitizer = Module("sanitizer", tmp.Sanitizer, {
             function (key, event, arg) {
                 if (event == name)
                     params.action.apply(params, arg);
-            }, Module.callerGlobal(params.action));
+            }, Class.objectGlobal(params.action));
 
         if (params.privateEnter || params.privateLeave)
             storage.addObserver("private-mode",
@@ -111,7 +111,7 @@ const Sanitizer = Module("sanitizer", tmp.Sanitizer, {
                     let meth = params[arg ? "privateEnter" : "privateLeave"];
                     if (meth)
                         meth.call(params);
-                }, Module.callerGlobal(params.action));
+                }, Class.objectGlobal(params.action));
     },
 
     observe: {