diff --git a/install-dev/sql/db.sql b/install-dev/sql/db.sql
index 030dca94b..03e8ea8a1 100644
--- a/install-dev/sql/db.sql
+++ b/install-dev/sql/db.sql
@@ -333,7 +333,7 @@ CREATE TABLE `PREFIX_category_product` (
   `id_category` int(10) unsigned NOT NULL,
   `id_product` int(10) unsigned NOT NULL,
   `position` int(10) unsigned NOT NULL default '0',
-  KEY `category_product_index` (`id_category`,`id_product`),
+  UNIQUE KEY `category_product_index` (`id_category`,`id_product`),
   INDEX (`id_product`)
 ) ENGINE=ENGINE_TYPE DEFAULT CHARSET=utf8;