diff --git a/content/buffer.js b/content/buffer.js
index 41b63e95..e763377d 100644
--- a/content/buffer.js
+++ b/content/buffer.js
@@ -797,18 +797,33 @@ function Buffer() //{{{
             argCount: "0"
         });
 
+    // TODO: we're prompted if download.useDownloadDir isn't set and no arg specified - intentional?
     commands.add(["sav[eas]", "w[rite]"],
         "Save current document to disk",
         function (args, special)
         {
-            args = args.string;
-
             let doc = window.content.document;
-            let file = io.getFile(args || "");
-            if (args && file.exists() && !special)
-                return liberator.echoerr("E13: File exists (add ! to override)");
+            let chosenData = null;
+            let filename = args.arguments[0];
 
+            if (filename)
+            {
+                let file = io.getFile(filename);
+
+                if (file.exists() && !special)
+                {
+                    liberator.echoerr("E13: File exists (add ! to override)");
+                    return;
+                }
+
+                chosenData = { file: file, uri: makeURI(doc.location.href, doc.characterSet) };
+            }
+
+            // if browser.download.useDownloadDir = false then the "Save As"
+            // dialog is used with this as the default directory
+            // TODO: if we're going to do this shouldn't it be done in setCWD or the value restored?
             options.setPref("browser.download.lastDir", io.getCurrentDirectory());
+
             try
             {
                 var contentDisposition = window.content
@@ -818,12 +833,11 @@ function Buffer() //{{{
             } catch (e) {}
 
             internalSave(doc.location.href, doc, null, contentDisposition,
-                doc.contentType, false, null,
-                args && { file: file, uri: makeURI(doc.location.href, doc.characterSet) },
-                doc.referrer ? makeURI(doc.referrer) : null,
-                true);
+                doc.contentType, false, null, chosenData, doc.referrer ?
+                makeURI(doc.referrer) : null, true);
         },
         {
+            argCount: "?",
             bang: true,
             completer: function (filter) completion.file(filter)
         });
diff --git a/content/completion.js b/content/completion.js
index 8b2ff7ac..f44fc856 100644
--- a/content/completion.js
+++ b/content/completion.js
@@ -897,28 +897,32 @@ function Completion() //{{{
         // if "tail" is true, only return names without any directory components
         file: function file(filter, tail)
         {
-            let [matches, dir, compl] = filter.match(/^((?:.*[\/\\])?)(.*?)$/);
+            let [, dir, compl] = filter.match(/^((?:.*[\/\\])?)(.*?)$/);
             // dir == "" is expanded inside readDirectory to the current dir
 
             let generate = function ()
             {
-                var files = [], mapped = [];
+                let files = [], mapped = [];
 
                 try
                 {
+                    dir = dir.replace("\\ ", " ", "g");
                     files = io.readDirectory(dir, true);
 
                     if (options["wildignore"])
                     {
-                        var wigRegexp = new RegExp("(^" + options["wildignore"].replace(",", "|", "g") + ")$");
+                        let wigRegexp = RegExp("(^" + options["wildignore"].replace(",", "|", "g") + ")$");
 
                         files = files.filter(function (f) f.isDirectory() || !wigRegexp.test(f.leafName))
                     }
 
-                    mapped = files.map(function (file) [tail ? file.leafName : (dir + file.leafName),
-                                                        file.isDirectory() ? "Directory" : "File"]);
+                    mapped = files.map(
+                        function (file) [(tail ? file.leafName : dir + file.leafName).replace(" ", "\\ ", "g"),
+                            file.isDirectory() ? "Directory" : "File"]
+                    );
                 }
                 catch (e) {}
+
                 return mapped;
             };
 
diff --git a/content/io.js b/content/io.js
index d7229cfa..45e6b0a6 100644
--- a/content/io.js
+++ b/content/io.js
@@ -218,23 +218,17 @@ function IO() //{{{
         "Write current key mappings and changed options to the config file",
         function (args, special)
         {
-            args = args.string;
-
             // TODO: "E172: Only one file name allowed"
-            var filename;
-            if (args)
-                filename = args;
-            else
-                filename = "~/" + (WINDOWS ? "_" : ".") + EXTENSION_NAME + "rc";
+            let filename = args.arguments[0] || "~/" + (WINDOWS ? "_" : ".") + EXTENSION_NAME + "rc";
+            let file = io.getFile(filename);
 
-            var file = io.getFile(filename);
             if (file.exists() && !special)
             {
                 liberator.echoerr("E189: \"" + filename + "\" exists (add ! to override)");
                 return;
             }
 
-            var line = "\" " + liberator.version + "\n";
+            let line = "\" " + liberator.version + "\n";
             line += "\" Mappings\n";
 
             [[[modes.NORMAL], ""],
@@ -286,6 +280,7 @@ function IO() //{{{
             }
         },
         {
+            argCount: "?",
             bang: true,
             completer: function (filter) completion.file(filter, true)
         });
@@ -348,18 +343,11 @@ function IO() //{{{
         "Read Ex commands from a file",
         function (args, special)
         {
-            args = args.string;
-
-            // FIXME: implement proper filename quoting - "E172: Only one file name allowed"
-            if (!args)
-            {
-                liberator.echoerr("E471: Argument required");
-                return;
-            }
-
-            io.source(args, special);
+            // FIXME: "E172: Only one file name allowed"
+            io.source(args.arguments[0], special);
         },
         {
+            argCount: "1",
             bang: true,
             completer: function (filter) completion.file(filter, true)
         });
@@ -414,7 +402,7 @@ function IO() //{{{
             // expand "~" to VIMPERATOR_HOME or HOME (USERPROFILE or HOMEDRIVE\HOMEPATH on Windows if HOME is not set)
             if (/^~/.test(path))
             {
-                var home = environmentService.get("VIMPERATOR_HOME");
+                let home = environmentService.get("VIMPERATOR_HOME");
 
                 if (!home)
                     home = environmentService.get("HOME");
@@ -434,6 +422,8 @@ function IO() //{{{
                 function (m, n1, n2, i, s) environmentService.get((n1 || n2), "$1")
             );
 
+            path = path.replace("\\ ", " ", "g");
+
             return path;
         },