diff --git a/common/content/dactyl.js b/common/content/dactyl.js
index 1d27671f..986d93e7 100644
--- a/common/content/dactyl.js
+++ b/common/content/dactyl.js
@@ -208,14 +208,16 @@ var Dactyl = Module("dactyl", XPCOM(Ci.nsISupportsWeakReference, ModuleBase), {
                 },
                 options: params.options || []
             });
+
         if (params.index)
             this.indices[params.index] = function () {
                 let results = array((params.iterateIndex || params.iterate).call(params, commands.get(name).newArgs()))
                         .array.sort(function (a, b) String.localeCompare(a.name, b.name));
 
+                let tags = services["dactyl:"].HELP_TAGS;
                 for (let obj in values(results)) {
                     let res = dactyl.generateHelp(obj, null, null, true);
-                    if (!set.has(services["dactyl:"].HELP_TAGS, obj.helpTag))
+                    if (!set.has(tags, obj.helpTag))
                         res[1].@tag = obj.helpTag;
 
                     yield res;
@@ -794,7 +796,7 @@ var Dactyl = Module("dactyl", XPCOM(Ci.nsISupportsWeakReference, ModuleBase), {
 
             default xml namespace = NS;
 
-            overlayMap["index"] = function () ['text/xml;charset=UTF-8',
+            overlayMap["index"] = ['text/xml;charset=UTF-8',
                 '<?xml version="1.0"?>\n' +
                 '<overlay xmlns="' + NS + '">\n' +
                 unescape(encodeURI( // UTF-8 handling hack.
@@ -804,6 +806,7 @@ var Dactyl = Module("dactyl", XPCOM(Ci.nsISupportsWeakReference, ModuleBase), {
                     }</dl>, <>{"\n\n"}</>))) +
                 '\n</overlay>'];
 
+            addTags("index", util.httpGet("dactyl://help-overlay/index").responseXML);
             addTags("index", util.httpGet("dactyl://help/index").responseXML);
 
             this.helpInitialized = true;
diff --git a/common/modules/options.jsm b/common/modules/options.jsm
index 7c3403a5..6beff5e6 100644
--- a/common/modules/options.jsm
+++ b/common/modules/options.jsm
@@ -895,7 +895,12 @@ var Options = Module("options", {
 
         ret.optionValue = ret.option.get(ret.scope);
 
-        ret.values = ret.option.parse(ret.value);
+        try {
+            ret.values = ret.option.parse(ret.value);
+        }
+        catch (e) {
+            ret.error = e;
+        }
 
         return ret;
     },
@@ -1095,21 +1100,23 @@ var Options = Module("options", {
                 return completion.option(context, opt.scope, prefix);
             }
 
-            let option = opt.option;
-            if (!option) {
-                context.message = "No such option: " + opt.name;
-                context.highlight(0, opt.name.length, "SPELLCHECK");
-                return;
+            function error(length, message) {
+                context.message = message;
+                context.highlight(0, length, "SPELLCHECK");
             }
 
+            let option = opt.option;
+            if (!option)
+                return error(opt.name.length, "No such option: " + opt.name);
+
             context.advance(context.filter.indexOf("="));
-            if (option.type == "boolean") {
-                context.message = "Trailing characters";
-                context.highlight(0, context.filter.length, "SPELLCHECK");
-                return;
-            }
+            if (option.type == "boolean")
+                return error(context.filter.length, "Trailing characters");
 
             context.advance(1);
+            if (opt.error)
+                return error(context.filter.length, opt.error);
+
             if (opt.get || opt.reset || !option || prefix)
                 return null;