diff --git a/src/shell-screenshot.c b/src/shell-screenshot.c
index 2914e0705..da75ce09c 100644
--- a/src/shell-screenshot.c
+++ b/src/shell-screenshot.c
@@ -217,7 +217,7 @@ do_grab_screenshot (_screenshot_data *screenshot_data,
   backend = clutter_get_default_backend ();
   context = clutter_backend_get_cogl_context (backend);
 
-  screenshot_data->image = cairo_image_surface_create (CAIRO_FORMAT_RGB24,
+  screenshot_data->image = cairo_image_surface_create (CAIRO_FORMAT_ARGB32,
                                                        width, height);
 
 
@@ -234,6 +234,8 @@ do_grab_screenshot (_screenshot_data *screenshot_data,
                                             x, y,
                                             COGL_READ_PIXELS_COLOR_BUFFER,
                                             bitmap);
+
+  cairo_surface_mark_dirty (screenshot_data->image);
   cogl_object_unref (bitmap);
 }