diff --git a/common/content/mappings.js b/common/content/mappings.js
index d409ba79..d47501b3 100644
--- a/common/content/mappings.js
+++ b/common/content/mappings.js
@@ -59,7 +59,7 @@ Map.prototype = {
 
     execute: function (motion, count, argument)
     {
-        var args = [];
+        let args = [];
 
         if (this.flags & Mappings.flags.MOTION)
             args.push(motion);
@@ -98,7 +98,7 @@ function Mappings() //{{{
 
     function addMap(map, userMap)
     {
-        var where = userMap ? user : main;
+        let where = userMap ? user : main;
         map.modes.forEach(function (mode) {
                 if (!(mode in where))
                     where[mode] = [];
@@ -108,7 +108,7 @@ function Mappings() //{{{
 
     function getMap(mode, cmd, stack)
     {
-        var maps = stack[mode] || [];
+        let maps = stack[mode] || [];
 
         for (let [,map] in Iterator(maps))
         {
@@ -121,8 +121,8 @@ function Mappings() //{{{
 
     function removeMap(mode, cmd)
     {
-        var maps = user[mode] || [];
-        var names;
+        let maps = user[mode] || [];
+        let names;
 
         for (let [i, map] in Iterator(maps))
         {
@@ -305,7 +305,7 @@ function Mappings() //{{{
         addUserMap: function (modes, keys, description, action, extra)
         {
             keys = keys.map(expandLeader);
-            var map = new Map(modes, keys, description || "User defined mapping", action, extra);
+            let map = new Map(modes, keys, description || "User defined mapping", action, extra);
 
             // remove all old mappings to this key sequence
             for (let [,name] in Iterator(map.names))
@@ -353,7 +353,7 @@ function Mappings() //{{{
 
         getMapLeader: function ()
         {
-            var leaderRef = liberator.variableReference("mapleader");
+            let leaderRef = liberator.variableReference("mapleader");
             return leaderRef[0] ? leaderRef[0][leaderRef[1]] : "\\";
         },
 
diff --git a/common/content/modes.js b/common/content/modes.js
index e79a67f4..fc4195c5 100644
--- a/common/content/modes.js
+++ b/common/content/modes.js
@@ -54,13 +54,13 @@ const modes = (function () //{{{
             return "-- PASS THROUGH --";
 
         // when recording a macro
-        var macromode = "";
+        let macromode = "";
         if (modes.isRecording)
             macromode = "recording";
         else if (modes.isReplaying)
             macromode = "replaying";
 
-        var ext = "";
+        let ext = "";
         if (extended & modes.MENU) // TODO: desirable?
             ext += " (menu)";
         ext += " --" + macromode;
@@ -199,7 +199,7 @@ const modes = (function () //{{{
 
         pop: function (silent)
         {
-            var a = modeStack.pop();
+            let a = modeStack.pop();
             if (a)
                 this.set(a[0], a[1], silent);
             else
diff --git a/common/content/options.js b/common/content/options.js
index a1844a5f..0a244ab3 100644
--- a/common/content/options.js
+++ b/common/content/options.js
@@ -117,7 +117,7 @@ Option.prototype = {
             scope = this.scope;
         }
 
-        var aValue;
+        let aValue;
 
         if (liberator.has("tabs") && (scope & options.OPTION_SCOPE_LOCAL))
             aValue = tabs.options[this.name];
@@ -334,7 +334,7 @@ function Options() //{{{
                 prefContexts[prefContexts.length - 1][name] = val;
         }
 
-        var type = prefService.getPrefType(name);
+        let type = prefService.getPrefType(name);
         switch (typeof value)
         {
             case "string":
@@ -439,7 +439,7 @@ function Options() //{{{
 
             if (!args)
             {
-                var str =
+                let str =
                     <table>
                     {
                         template.map(liberator.globalVariables, function ([i, value]) {
@@ -460,20 +460,20 @@ function Options() //{{{
                 return;
             }
 
-            var matches;
+            let matches;
             // 1 - type, 2 - name, 3 - +-., 4 - expr
             if (matches = args.match(/([$@&])?([\w:]+)\s*([-+.])?=\s*(.+)/))
             {
                 if (!matches[1])
                 {
-                    var reference = liberator.variableReference(matches[2]);
+                    let reference = liberator.variableReference(matches[2]);
                     if (!reference[0] && matches[3])
                     {
                         liberator.echoerr("E121: Undefined variable: " + matches[2]);
                         return;
                     }
 
-                    var expr = liberator.evalExpression(matches[4]);
+                    let expr = liberator.evalExpression(matches[4]);
                     if (expr === undefined)
                     {
                         liberator.echoerr("E15: Invalid expression: " + matches[4]);
@@ -506,14 +506,14 @@ function Options() //{{{
             // 1 - name
             else if (matches = args.match(/^\s*([\w:]+)\s*$/))
             {
-                var reference = liberator.variableReference(matches[1]);
+                let reference = liberator.variableReference(matches[1]);
                 if (!reference[0])
                 {
                     liberator.echoerr("E121: Undefined variable: " + matches[1]);
                     return;
                 }
 
-                var value = reference[0][reference[1]];
+                let value = reference[0][reference[1]];
                 let prefix = typeof value == "number"   ? "#" :
                              typeof value == "function" ? "*" :
                                                           " ";
@@ -567,9 +567,9 @@ function Options() //{{{
             {
                 if (bang)
                 {
-                    var onlyNonDefault = false;
-                    var reset = false;
-                    var invertBoolean = false;
+                    let onlyNonDefault = false;
+                    let reset = false;
+                    let invertBoolean = false;
 
                     if (args[0] == "")
                     {
@@ -685,7 +685,6 @@ function Options() //{{{
             completer: function (context, args, modifiers)
             {
                 let filter = context.filter;
-                var optionCompletions = [];
 
                 if (args.bang) // list completions for about:config entries
                 {
@@ -758,15 +757,15 @@ function Options() //{{{
         "Delete a variable",
         function (args)
         {
-            //var names = args.split(/ /);
+            //let names = args.split(/ /);
             //if (typeof names == "string") names = [names];
 
-            //var length = names.length;
+            //let length = names.length;
             //for (let i = 0, name = names[i]; i < length; name = names[++i])
             for (let [,name] in args)
             {
-                var name = args[i];
-                var reference = liberator.variableReference(name);
+                let name = args[i];
+                let reference = liberator.variableReference(name);
                 if (!reference[0])
                 {
                     if (!args.bang)
@@ -894,7 +893,7 @@ function Options() //{{{
             if (!filter)
                 filter = "";
 
-            var prefArray = prefService.getChildList("", { value: 0 });
+            let prefArray = prefService.getChildList("", { value: 0 });
             prefArray.sort();
             let prefs = function () {
                 for each (let pref in prefArray)
diff --git a/common/content/ui.js b/common/content/ui.js
index 44061a55..8eadbf3e 100644
--- a/common/content/ui.js
+++ b/common/content/ui.js
@@ -809,7 +809,7 @@ function CommandLine() //{{{
             command.description,
             function (args)
             {
-                var str = echoArgumentToString(args.string, true);
+                let str = echoArgumentToString(args.string, true);
                 if (str != null)
                     command.action(str);
             },
diff --git a/vimperator/NEWS b/vimperator/NEWS
index f982feda..4fd0ddaf 100644
--- a/vimperator/NEWS
+++ b/vimperator/NEWS
@@ -20,6 +20,7 @@
     * IMPORTANT: renamed Startup and Quit autocmd events to VimperatorEnter and
       VimperatorLeave respectively
     * IMPORTANT: 'verbose' is now by default at 1, set to 0 to not show any status messages
+    * IMPORTANT: option values containing whitespace must now be quoted E.g. :set editor=gvim\ -f
 
     * :hardcopy now supports output redirection to a file on Unix and MacUnix
     * add ";f" extended hint mode to focus a frame