diff --git a/common/content/tabs.js b/common/content/tabs.js
index 79abe0a6..1c4b24f8 100644
--- a/common/content/tabs.js
+++ b/common/content/tabs.js
@@ -961,24 +961,24 @@ var Tabs = Module("tabs", {
     options: function () {
         options.add(["showtabline", "stal"],
             "Define when the tab bar is visible",
-            "number", config.defaults["showtabline"],
+            "string", config.defaults["showtabline"],
             {
                 setter: function (value) {
-                    if (value == 0)
+                    if (value === "never")
                         tabs.tabStyle.enabled = true;
                     else {
-                        prefs.safeSet("browser.tabs.autoHide", value == 1,
+                        prefs.safeSet("browser.tabs.autoHide", value === "multitab",
                                       "See 'showtabline' option.");
                         tabs.tabStyle.enabled = false;
                     }
-                    if (value != 1 || !dactyl.has("Gecko2"))
+                    if (value !== "multitab" || !dactyl.has("Gecko2"))
                         config.tabStrip.collapsed = false;
                     return value;
                 },
                 completer: function (context) [
-                    ["0", "Never show tab bar"],
-                    ["1", "Show tab bar only if more than one tab is open"],
-                    ["2", "Always show tab bar"]
+                    ["never",    "Never show tab bar"],
+                    ["multitab", "Show tab bar when there are multiple tabs"],
+                    ["always",   "Always show tab bar"]
                 ]
             });
 
diff --git a/common/locale/en-US/options.xml b/common/locale/en-US/options.xml
index dfa8480c..86b8e01e 100644
--- a/common/locale/en-US/options.xml
+++ b/common/locale/en-US/options.xml
@@ -1382,6 +1382,22 @@
 <item>
     <tags>'stal' 'showtabline'</tags>
     <spec>'showtabline' 'stal'</spec>
+    <type>string</type>
+    <default>always</default>
+    <description>
+        <p>Define when the tab bar is visible.</p>
+
+        <dl>
+            <dt>always</dt> <dd>Always show tab bar</dd>
+            <dt>multitab</dt> <dd>Show tab bar when there are multiple tabs</dd>
+            <dt>never</dt> <dd>Never show tab bar</dd>
+        </dl>
+    </description>
+</item>
+
+</item>
+
+
     <type>number</type>
     <default>2</default>
     <description>
diff --git a/common/modules/base.jsm b/common/modules/base.jsm
index 3b3472eb..bd4bd6b2 100644
--- a/common/modules/base.jsm
+++ b/common/modules/base.jsm
@@ -16,11 +16,15 @@ if (!JSMLoader)
 
                 for each (let prop in Object.getOwnPropertyNames(global))
                     try {
-                        if (!set.has(this.builtin, prop) &&
-                            [this, set].indexOf(Object.getOwnPropertyDescriptor(global, prop).value) < 0)
-                            delete global[prop];
+                        if (!(prop in this.builtin) &&
+                            [this, set].indexOf(Object.getOwnPropertyDescriptor(global, prop).value) < 0 &&
+                            !global.__lookupGetter__(prop))
+                            global[prop] = null;
+                    }
+                    catch (e) {
+                        dump("Deleting property " + prop + " on " + url + ":\n    " + e + "\n");
+                        Components.utils.reportError(e);
                     }
-                    catch (e) {}
 
                 Components.classes["@mozilla.org/moz/jssubscript-loader;1"]
                           .getService(Components.interfaces.mozIJSSubScriptLoader)
diff --git a/pentadactyl/NEWS b/pentadactyl/NEWS
index db003f7f..4cac10e1 100644
--- a/pentadactyl/NEWS
+++ b/pentadactyl/NEWS
@@ -102,7 +102,7 @@
         a boolean.
       - 'mapleader' is now an option rather than a :let
         variable.
-      - 'showstatuslinks' is now a string option.
+      - 'showstatuslinks' and 'showtabline' are now string options.
     * IMPORTANT: Command script files now use the *.penta file extension.
     * IMPORTANT: Plugins are now loaded from the 'plugins/'
       directory in 'runtimepath' rather than 'plugin/'.
diff --git a/pentadactyl/content/config.js b/pentadactyl/content/config.js
index d2d8b832..f8ca97fa 100644
--- a/pentadactyl/content/config.js
+++ b/pentadactyl/content/config.js
@@ -6,7 +6,7 @@
 // given in the LICENSE.txt file included with this file.
 "use strict";
 
-const Config = Module("config", ConfigBase, {
+var Config = Module("config", ConfigBase, {
     name: "pentadactyl",
     appName: "Pentadactyl",
     idName: "PENTADACTYL",
@@ -174,7 +174,7 @@ const Config = Module("config", ConfigBase, {
     defaults: {
         complete: "slf",
         guioptions: "bCrs",
-        showtabline: 2,
+        showtabline: "always",
         titlestring: "Pentadactyl"
     },