diff --git a/blocktopmenu.php b/blocktopmenu.php
index a7015a3..cc31055 100644
--- a/blocktopmenu.php
+++ b/blocktopmenu.php
@@ -579,7 +579,7 @@ protected function generateCategoriesOption($categories, $items_to_skip = null)
         foreach ($categories as $key => $category) {
             if (isset($items_to_skip) /*&& !in_array('CAT'.(int)$category['id_category'], $items_to_skip)*/) {
                 $shop = (object) Shop::getShop((int)$category['id_shop']);
-                $html .= '<option value="CAT'.(int)$category['id_category'].'">'
+                $html .= '<option value="CAT'.(int)$category['id_category'].'"'.((int)$category['level_depth'] == 0 ? ' disabled="disabled"' : '').'>'
                     .str_repeat('&nbsp;', $this->spacer_size * (int)$category['level_depth']).$category['name'].' ('.$shop->name.')</option>';
             }
 
diff --git a/views/templates/admin/_configure/helpers/form/form.tpl b/views/templates/admin/_configure/helpers/form/form.tpl
index 80f23a5..f9b66f5 100644
--- a/views/templates/admin/_configure/helpers/form/form.tpl
+++ b/views/templates/admin/_configure/helpers/form/form.tpl
@@ -39,7 +39,7 @@ $("#items").closest('form').on('submit', function(e) {
 	$("#items option").prop('selected', true);
 });
 $("#addItem").click(add);
-$("#availableItems").dblclick(add);
+$("#availableItems option:not([disabled])").dblclick(add);
 $("#removeItem").click(remove);
 $("#items").dblclick(remove);
 function add()
@@ -56,6 +56,9 @@ function add()
 			text = '{l s="Product ID #" mod='blocktopmenu' js=1}'+val;
 			val = "PRD"+val;
 		}
+		if($("#items option[value="+val+"]").length != 0){
+			return false;
+		}
 		$("#items").append('<option value="'+val+'" selected="selected">'+text+'</option>');
 	});
 	serialize();