diff --git a/AUTHORS b/AUTHORS
index 818d7af..8bb3fdf 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -1 +1,2 @@
 Gustavo Sverzut Barbieri <barbieri@gmail.com>
+Bruno Dilly <bdilly@profusion.mobi>
diff --git a/src/bin/main.c b/src/bin/main.c
index 2aa7fcc..7df9f04 100644
--- a/src/bin/main.c
+++ b/src/bin/main.c
@@ -31,6 +31,7 @@ struct _Zone {
    Evas_Object *display_pos;
    Evas_Object *cmdbox;
    Evas_Object *help_popup;
+   Evas_Object *error_popup;
    Ecore_Idler *del_help_popup_idler;
    struct {
       Evas_Object *frame;
@@ -1434,6 +1435,47 @@ zone_zoom_pre_setup(Zone *zone)
    zone->zoom.ready = EINA_FALSE;
 }
 
+static void
+_error_popup_hide_cb(void *data, Evas_Object *o EINA_UNUSED, void *event EINA_UNUSED)
+{
+   Zone *zone = data;
+   evas_object_del(zone->error_popup);
+   zone->error_popup = NULL;
+}
+
+static void
+show_error_popup(Zone *zone, const char *str)
+{
+   Evas_Object *popup, *msg;
+
+   if (zone->error_popup) return;
+
+   popup = elm_popup_add(zone->win);
+   elm_popup_content_text_wrap_type_set(popup, ELM_WRAP_MIXED);
+
+   elm_object_part_text_set(popup, "title,text", "ERuler");
+
+   msg = elm_entry_add(popup);
+   elm_entry_editable_set(msg, EINA_FALSE);
+
+#if (ELM_VERSION_MAJOR >= 1) && (ELM_VERSION_MINOR >= 8)
+   elm_scroller_policy_set(msg, ELM_SCROLLER_POLICY_OFF,
+                           ELM_SCROLLER_POLICY_AUTO);
+#else
+   elm_entry_scrollbar_policy_set(msg, ELM_SCROLLER_POLICY_OFF,
+                                  ELM_SCROLLER_POLICY_AUTO);
+#endif
+
+   elm_object_text_set(msg, str);
+   elm_object_content_set(popup, msg);
+
+   elm_popup_timeout_set(popup, 3);
+   evas_object_smart_callback_add(popup, "timeout", _error_popup_hide_cb, zone);
+
+   evas_object_show(popup);
+   zone->error_popup = popup;
+}
+
 static void
 _popup_dismiss_cb(void *data, Evas_Object *o EINA_UNUSED, void *event EINA_UNUSED)
 {
@@ -1560,11 +1602,15 @@ _create_ruler_cmdbox_activated(void *data, Evas_Object *o, void *event_info EINA
 
    if (sscanf(str, "%d %d %d %d", &x, &y, &w, &h) != 4)
      {
+        show_error_popup(zone,
+                         "Error: Invalid creation format. Expected 'x y w h'");
         ERR("Invalid creation format. Expected 'x y w h', got '%s'", str);
         goto end;
      }
    if (w < 1 || h < 1)
      {
+        show_error_popup(zone,
+                         "Error: Invalid size. w and h must be positive.");
         ERR("Invalid size: %dx%d", w, h);
         goto end;
      }