diff --git a/src/window.vala b/src/window.vala
index 4dcde6f..92451ed 100644
--- a/src/window.vala
+++ b/src/window.vala
@@ -1,159 +1,166 @@
 public class WriteAs.MainWindow : Gtk.ApplicationWindow {
     private Gtk.TextView canvas;
 
     private bool dark_mode = false;
     private string font = "Lora, 'Palatino Linotype',"
             + "'Book Antiqua', 'New York', 'DejaVu serif', serif";
 
     construct {
         construct_toolbar();
         build_keyboard_shortcuts();
 
         canvas = new Gtk.TextView();
         add(canvas);
 
         adjust_text_style();
     }
 
     public MainWindow(Gtk.Application app) {
         set_application(app);
 
         set_default_size(800, 600);
     }
 
     private void construct_toolbar() {
         var header = new Gtk.HeaderBar();
         header.title = "";
         header.show_close_button = true;
         set_titlebar(header);
 
         var darkmode_button = new Gtk.ToggleButton();
         darkmode_button.tooltip_text = _("Toggle dark theme");
         // NOTE the fallback icon is a bit of a meaning stretch, but it works.
         var icon_theme = Gtk.IconTheme.get_default();
         darkmode_button.image = new Gtk.Image.from_icon_name(
                 icon_theme.has_icon("writeas-bright-dark") ?
                     "writeas-bright-dark" : "weather-clear-night",
                 Gtk.IconSize.SMALL_TOOLBAR);
         darkmode_button.draw_indicator = false;
         var settings = Gtk.Settings.get_default();
         darkmode_button.toggled.connect(() => {
             settings.gtk_application_prefer_dark_theme = darkmode_button.active;
             dark_mode = darkmode_button.active;
             adjust_text_style();
         });
         header.pack_end(darkmode_button);
 
         var fonts = new Gtk.MenuButton();
         fonts.tooltip_text = _("Change document font");
         fonts.image = new Gtk.Image.from_icon_name("font-x-generic", Gtk.IconSize.SMALL_TOOLBAR);
         fonts.popup = new Gtk.Menu();
         header.pack_start(fonts);
 
         build_fontoption(fonts.popup, _("Serif"), font);
         build_fontoption(fonts.popup, _("Sans-serif"), "'Open Sans', 'Segoe UI',"
                 + "Tahoma, Arial, sans-serif");
         build_fontoption(fonts.popup, _("Monospace"), "Hack, consolas," +
                 "Menlo-Regular, Menlo, Monaco, 'ubuntu mono', monospace");
         fonts.popup.show_all();
     }
 
     private void build_fontoption(Gtk.Menu menu, string label, string families) {
         var option = new Gtk.MenuItem.with_label(label);
         option.activate.connect(() => {
             this.font = families;
             adjust_text_style();
         });
 
         var styles = option.get_style_context();
         var provider = new Gtk.CssProvider();
         try {
             provider.load_from_data("* {font: %s;}".printf(families));
             styles.add_provider(provider, Gtk.STYLE_PROVIDER_PRIORITY_APPLICATION);
         } catch (Error e) {
             warning(e.message);
         }
 
         menu.add(option);
     }
 
     private Gtk.CssProvider cur_styles = null;
     private void adjust_text_style() {
         try {
             var styles = canvas.get_style_context();
             if (cur_styles != null) styles.remove_provider(cur_styles);
 
             var css = "* {font: %s; padding: 20px;}".printf(font);
             if (dark_mode) {
                 // Try to detect whether the system provided a better dark mode.
                 var text_color = styles.get_color(Gtk.StateFlags.ACTIVE);
                 double h, s, v;
                 Gtk.rgb_to_hsv(text_color.red, text_color.green, text_color.blue,
                         out h, out s, out v);
 
                 if (v < 0.5) css += "* {background: black; color: white;}";
             }
             cur_styles = new Gtk.CssProvider();
             cur_styles.load_from_data(css);
 
             styles.add_provider(cur_styles, Gtk.STYLE_PROVIDER_PRIORITY_APPLICATION);
         } catch (Error e) {
             warning(e.message);
         }
     }
 
     /* --- */
 
     private void build_keyboard_shortcuts() {
         /* These operations are not exposed to the UI as buttons,
             as most people are very familiar with them and they are not the
             focus of this app. */
         var accels = new Gtk.AccelGroup();
 
         accels.connect(Gdk.Key.S, Gdk.ModifierType.CONTROL_MASK,
                 Gtk.AccelFlags.VISIBLE | Gtk.AccelFlags.LOCKED,
                 (g,a,k,m) => save_as());
         accels.connect(Gdk.Key.S,
                 Gdk.ModifierType.CONTROL_MASK | Gdk.ModifierType.SHIFT_MASK,
                 Gtk.AccelFlags.VISIBLE | Gtk.AccelFlags.LOCKED,
                 (g,a,k,m) => save_as());
         accels.connect(Gdk.Key.O, Gdk.ModifierType.CONTROL_MASK,
                 Gtk.AccelFlags.VISIBLE | Gtk.AccelFlags.LOCKED, (g, a, k, m) => {
             try {
                 uint8[] text;
                 var file = prompt_file(Gtk.FileChooserAction.OPEN, _("_Open"));
                 file.load_contents(null, out text, null);
                 canvas.buffer.text = (string) text;
             } catch (Error e) {
                 // It's fine...
             }
             return true;
         });
 
         add_accel_group(accels);
     }
 
     private bool save_as() {
-        // TODO
+        try {
+        var file = prompt_file(Gtk.FileChooserAction.SAVE, _("_Save as"));
+        file.replace_contents(canvas.buffer.text.data, null, false,
+                FileCreateFlags.PRIVATE | FileCreateFlags.REPLACE_DESTINATION,
+                null);
+        } catch (Error e) {
+            // It's fine...
+        }
         return true;
     }
 
     private File prompt_file(Gtk.FileChooserAction mode, string action)
             throws UserCancellable {
         var file_chooser = new Gtk.FileChooserDialog(action, this, mode,
               _("_Cancel"), Gtk.ResponseType.CANCEL,
               action, Gtk.ResponseType.ACCEPT);
 
         file_chooser.select_multiple = false;
         var filter = new Gtk.FileFilter();
         filter.add_mime_type("text/plain");
         file_chooser.set_filter(filter);
 
         var resp = file_chooser.run();
         file_chooser.close();
         if (resp == Gtk.ResponseType.ACCEPT) return file_chooser.get_file();
         else throw new UserCancellable.USER_CANCELLED("FileChooserDialog");
     }
 }
 
 errordomain WriteAs.UserCancellable {USER_CANCELLED}