diff --git a/src/ag-app.c b/src/ag-app.c
index 916b6c3..6203674 100644
--- a/src/ag-app.c
+++ b/src/ag-app.c
@@ -78,10 +78,10 @@ static void
 preferences_cb(GSimpleAction *action, GVariant *parameter, gpointer user_data)
 {
     AgApp *app = AG_APP(user_data);
-    GtkWindow *window;
 
-    window = ag_app_peek_first_window(app);
-    ag_preferences_show_dialog(window);
+    ag_preferences_show_dialog(
+            gtk_application_get_active_window(GTK_APPLICATION(app))
+        );
 }
 
 static void
@@ -97,26 +97,29 @@ about_cb(GSimpleAction *action, GVariant *parameter, gpointer user_data)
         NULL
     };
     const gchar *translator_credits = _("translator_credits");
+    AgApp       *app                = AG_APP(user_data);
 
     /* i18n: Please don't translate "Astrognome" (it's marked as translatable
      * for transliteration only */
-    gtk_show_about_dialog(NULL,
-                          "name", _("Astrognome"),
-                          "version", PACKAGE_VERSION,
-                          "comments", _("Astrologers' software for GNOME"),
-                          "authors", authors,
-                          "artists", artists,
-                          "translator_credits", ((strcmp(
-                                                         translator_credits,
-                                                         "translator_credits"
-                                                     ) != 0)
-                                                 ? translator_credits
-                                                 : NULL),
-                          "website", PACKAGE_URL,
-                          "website-label", _("Astrognome Website"),
-                          "license-type", GTK_LICENSE_GPL_3_0,
-                          "logo-icon-name", PACKAGE_TARNAME,
-                          NULL);
+    gtk_show_about_dialog(
+            gtk_application_get_active_window(GTK_APPLICATION(app)),
+            "name", _("Astrognome"),
+            "version", PACKAGE_VERSION,
+            "comments", _("Astrologers' software for GNOME"),
+            "authors", authors,
+            "artists", artists,
+            "translator_credits", ((strcmp(
+                                           translator_credits,
+                                           "translator_credits"
+                                       ) != 0)
+                                   ? translator_credits
+                                   : NULL),
+            "website", PACKAGE_URL,
+            "website-label", _("Astrognome Website"),
+            "license-type", GTK_LICENSE_GPL_3_0,
+            "logo-icon-name", PACKAGE_TARNAME,
+            NULL
+        );
 }
 
 static void
@@ -158,7 +161,7 @@ ag_app_import_file(AgApp *app, GFile *file, AgAppImportType type)
 
     if (chart == NULL) {
         ag_app_message_dialog(
-                NULL,
+                gtk_application_get_active_window(GTK_APPLICATION(app)),
                 GTK_MESSAGE_ERROR,
                 "Error while loading: %s",
                 err->message
@@ -183,6 +186,7 @@ ag_app_import_cb(GSimpleAction *action, GVariant *parameter, gpointer user_data)
     GSList          *filenames   = NULL;
     const gchar     *target_type = g_variant_get_string(parameter, NULL);
     AgAppImportType type         = AG_APP_IMPORT_NONE;
+    AgApp           *app         = AG_APP(user_data);
 
     if (strncmp("agc", target_type, 3) == 0) {
         type = AG_APP_IMPORT_AGC;
@@ -194,12 +198,14 @@ ag_app_import_cb(GSimpleAction *action, GVariant *parameter, gpointer user_data)
         g_error("Unknown import type!");
     }
 
-    fs = gtk_file_chooser_dialog_new(_("Select charts"),
-                                     NULL,
-                                     GTK_FILE_CHOOSER_ACTION_OPEN,
-                                     _("_Cancel"), GTK_RESPONSE_CANCEL,
-                                     _("_Import"), GTK_RESPONSE_ACCEPT,
-                                     NULL);
+    fs = gtk_file_chooser_dialog_new(
+            _("Select charts"),
+            gtk_application_get_active_window(GTK_APPLICATION(app)),
+            GTK_FILE_CHOOSER_ACTION_OPEN,
+            _("_Cancel"), GTK_RESPONSE_CANCEL,
+            _("_Import"), GTK_RESPONSE_ACCEPT,
+            NULL
+        );
     gtk_file_chooser_add_filter(GTK_FILE_CHOOSER(fs), filter_all);
     gtk_file_chooser_add_filter(GTK_FILE_CHOOSER(fs), filter);
     gtk_file_chooser_set_filter(GTK_FILE_CHOOSER(fs), filter);
@@ -263,7 +269,7 @@ show_help(const gchar *topic, GtkWindow *parent)
 
     if (!gtk_show_uri(screen, uri, gtk_get_current_event_time(), &err)) {
         ag_app_message_dialog(
-                GTK_WIDGET(parent),
+                GTK_WINDOW(parent),
                 GTK_MESSAGE_WARNING,
                 "Unable to display help: %s",
                 err->message
@@ -462,8 +468,8 @@ ag_app_class_init(AgAppClass *klass)
     application_class->open    = ag_app_import;
 }
 
-gint
-ag_app_buttoned_dialog(GtkWidget      *window,
+GtkResponseType
+ag_app_buttoned_dialog(GtkWindow      *window,
                        GtkMessageType message_type,
                        const gchar    *message,
                        const gchar    *first_button_text,
@@ -475,9 +481,7 @@ ag_app_buttoned_dialog(GtkWidget      *window,
     GtkWidget   *dialog;
     GtkWindow   *parent = NULL;
 
-    if (window) {
-        parent = GTK_WINDOW(window);
-    }
+    g_return_val_if_fail(GTK_IS_WINDOW(window), GTK_RESPONSE_NONE);
 
     dialog = gtk_message_dialog_new(
             parent,
@@ -510,7 +514,7 @@ ag_app_buttoned_dialog(GtkWidget      *window,
 }
 
 void
-ag_app_message_dialog(GtkWidget      *window,
+ag_app_message_dialog(GtkWindow      *window,
                       GtkMessageType message_type,
                       gchar          *fmt, ...)
 {
diff --git a/src/ag-app.h b/src/ag-app.h
index 3738a35..faf90aa 100644
--- a/src/ag-app.h
+++ b/src/ag-app.h
@@ -53,12 +53,12 @@ void ag_app_run_action(AgApp                   *app,
                        gboolean                is_remote,
                        const AstrognomeOptions *options);
 
-gint ag_app_buttoned_dialog(GtkWidget      *window,
+gint ag_app_buttoned_dialog(GtkWindow      *window,
                             GtkMessageType message_type,
                             const gchar    *message,
                             const gchar    *first_button_text, ...);
 
-void ag_app_message_dialog(GtkWidget      *window,
+void ag_app_message_dialog(GtkWindow      *window,
                            GtkMessageType message_type,
                            gchar          *fmt, ...);
 
diff --git a/src/ag-window.c b/src/ag-window.c
index 1c750de..67f227a 100644
--- a/src/ag-window.c
+++ b/src/ag-window.c
@@ -422,7 +422,7 @@ ag_window_redraw_chart(AgWindow *window)
 
     if (svg_content == NULL) {
         ag_app_message_dialog(
-                GTK_WIDGET(window),
+                GTK_WINDOW(window),
                 GTK_MESSAGE_WARNING,
                 "Unable to draw chart: %s",
                 err->message
@@ -741,7 +741,7 @@ ag_window_export_svg(AgWindow *window, GError **err)
     // We should never enter here, but who knows...
     if (priv->chart == NULL) {
         ag_app_message_dialog(
-                GTK_WIDGET(window),
+                GTK_WINDOW(window),
                 GTK_MESSAGE_ERROR,
                 _("Chart cannot be calculated.")
             );
@@ -758,7 +758,7 @@ ag_window_export_svg(AgWindow *window, GError **err)
 
     if ((name == NULL) || (*name == 0)) {
         ag_app_message_dialog(
-                GTK_WIDGET(window),
+                GTK_WINDOW(window),
                 GTK_MESSAGE_ERROR,
                 _("You must enter a name before saving a chart.")
             );
@@ -809,7 +809,7 @@ ag_window_export_svg_action(GSimpleAction *action,
 
     if (err) {
         ag_app_message_dialog(
-                GTK_WIDGET(window),
+                GTK_WINDOW(window),
                 GTK_MESSAGE_ERROR,
                 "%s",
                 err->message
@@ -831,7 +831,7 @@ ag_window_export(AgWindow *window, GError **err)
     // We should never enter here, but who knows...
     if (priv->chart == NULL) {
         ag_app_message_dialog(
-                GTK_WIDGET(window),
+                GTK_WINDOW(window),
                 GTK_MESSAGE_ERROR,
                 _("Chart cannot be calculated.")
             );
@@ -848,7 +848,7 @@ ag_window_export(AgWindow *window, GError **err)
 
     if ((name == NULL) || (*name == 0)) {
         ag_app_message_dialog(
-                GTK_WIDGET(window),
+                GTK_WINDOW(window),
                 GTK_MESSAGE_ERROR,
                 _("You must enter a name before saving a chart.")
             );
@@ -900,7 +900,7 @@ ag_window_export_action(GSimpleAction *action,
 
     if (err) {
         ag_app_message_dialog(
-                GTK_WIDGET(window),
+                GTK_WINDOW(window),
                 GTK_MESSAGE_ERROR,
                 "%s", err->message
             );
@@ -934,7 +934,7 @@ ag_window_can_close(AgWindow *window, gboolean display_dialog)
                 gint response;
 
                 response = ag_app_buttoned_dialog(
-                        GTK_WIDGET(window),
+                        GTK_WINDOW(window),
                         GTK_MESSAGE_QUESTION,
                         _("Chart is not saved. Do you want to save it?"),
                         _("Save and close"), GTK_RESPONSE_YES,
@@ -947,7 +947,7 @@ ag_window_can_close(AgWindow *window, gboolean display_dialog)
                     case GTK_RESPONSE_YES:
                         if (!ag_db_save_chart(db, save_data, &err)) {
                             ag_app_message_dialog(
-                                    GTK_WIDGET(window),
+                                    GTK_WINDOW(window),
                                     GTK_MESSAGE_ERROR,
                                     "Unable to save chart: %s",
                                     err->message
@@ -1001,7 +1001,7 @@ ag_window_save_action(GSimpleAction *action,
 
         if (!ag_db_save_chart(db, save_data, &err)) {
             ag_app_message_dialog(
-                    GTK_WIDGET(window),
+                    GTK_WINDOW(window),
                     GTK_MESSAGE_ERROR,
                     _("Unable to save: %s"),
                     err->message
@@ -1160,7 +1160,7 @@ ag_window_new_chart_action(GSimpleAction *action,
 
     if (priv->chart) {
         ag_app_message_dialog(
-                GTK_WIDGET(window),
+                GTK_WINDOW(window),
                 GTK_MESSAGE_ERROR,
                 "This window already has a chart. " \
                 "This should not happen, " \
@@ -1282,7 +1282,7 @@ ag_window_delete_action(GSimpleAction *action,
 
         if (!ag_db_delete_chart(db, id, &err)) {
             ag_app_message_dialog(
-                    GTK_WIDGET(window),
+                    GTK_WINDOW(window),
                     GTK_MESSAGE_ERROR,
                     "Unable to delete chart: %s",
                     (err && err->message)
@@ -1417,7 +1417,7 @@ ag_window_list_item_activated_cb(GdMainView        *view,
 
     if (priv->saved_data != NULL) {
         ag_app_message_dialog(
-                GTK_WIDGET(window),
+                GTK_WINDOW(window),
                 GTK_MESSAGE_ERROR,
                 "Window chart is not saved. " \
                 "This is a bug, it should not happen here. " \
@@ -1436,7 +1436,7 @@ ag_window_list_item_activated_cb(GdMainView        *view,
                  row_id,
                  &err)) == NULL) {
         ag_app_message_dialog(
-                GTK_WIDGET(window),
+                GTK_WINDOW(window),
                 GTK_MESSAGE_ERROR,
                 "Could not open chart."
             );
@@ -1453,7 +1453,7 @@ ag_window_list_item_activated_cb(GdMainView        *view,
                  &err
             )) == NULL) {
         ag_app_message_dialog(
-                GTK_WIDGET(window),
+                GTK_WINDOW(window),
                 GTK_MESSAGE_ERROR,
                 "Error: %s",
                 err->message