diff --git a/FuncionesImaxMultiEAN.php b/FuncionesImaxMultiEAN.php
index b0d92c7..35fd65f 100644
--- a/FuncionesImaxMultiEAN.php
+++ b/FuncionesImaxMultiEAN.php
@@ -14,12 +14,20 @@ class FuncionesImaxMultiEAN {
 	
 	public function storeEAN($productId, $ean, $combinationId = 0) {
 		$sql = 'INSERT INTO ' . _DB_PREFIX_.$this->modulo->prefijo . "multiean (id_product, id_product_attribute, ean13) VALUES ('$productId', '$combinationId', '$ean')";
-		return Db::getInstance()->execute($sql);
+		try {
+			return Db::getInstance()->execute($sql);
+		} catch (Exception $e) {
+			return false;
+		}
 	}
 	
 	public function deleteEAN($productId, $ean, $combinationId = 0) {
 		$sql = 'DELETE FROM ' . _DB_PREFIX_ . $this->modulo->prefijo . "multiean WHERE id_product = '$productId' AND id_product_attribute = '$combinationId' AND ean13 = '$ean'";
-		return Db::getInstance()->execute($sql);
+		try {
+			return Db::getInstance()->execute($sql);
+		} catch (Exception $e) {
+			return false;
+		}
 	}
 
 	public function getProductByEan($ean) {
diff --git a/config.xml b/config.xml
index 5253431..571cec0 100644
--- a/config.xml
+++ b/config.xml
@@ -2,7 +2,7 @@
         <module>
             <name>imaxmultiean</name>
             <displayName><![CDATA[Gestor de EANs Múltiples]]></displayName>
-            <version><![CDATA[1.3]]></version>
+            <version><![CDATA[1.4]]></version>
             <description><![CDATA[Permite añadir y gestionar múltiples códigos EAN para cada producto y combinación.]]></description>
             <author><![CDATA[Informax]]></author>
             <tab><![CDATA[administration]]></tab>
diff --git a/imaxmultiean.php b/imaxmultiean.php
index cda2954..58af655 100644
--- a/imaxmultiean.php
+++ b/imaxmultiean.php
@@ -22,7 +22,7 @@ class ImaxMultiEAN extends Module {
         $this->name = 'imaxmultiean';
         $this->tab = 'administration';
         $this->path = _PS_MODULE_DIR_ . $this->name . '/';
-        $this->version = '1.3';
+        $this->version = '1.4';
         $this->author = 'Informax';
         $this->need_instance = 0;
         $this->idManual = '';
diff --git a/sql-install.php b/sql-install.php
index 479207e..b430265 100644
--- a/sql-install.php
+++ b/sql-install.php
@@ -6,7 +6,8 @@ $sql[] = "CREATE TABLE IF NOT EXISTS `"._DB_PREFIX_.self::prefijo."multiean` (
 	`id_product` INT(10) NOT NULL,
 	`id_product_attribute` INT(10) NOT NULL,
 	`ean13` VARCHAR(255) NOT NULL,
-	PRIMARY KEY (`id`)
+	PRIMARY KEY (`id`),
+	UNIQUE KEY `unique_ean_per_product_combination` (`id_product`, `ean13`)
         )
         COLLATE='utf8_general_ci'
         ENGINE=MyIsam;";
diff --git a/templates/hook/admin_products_extra.tpl b/templates/hook/admin_products_extra.tpl
index f7c9242..b7c8161 100644
--- a/templates/hook/admin_products_extra.tpl
+++ b/templates/hook/admin_products_extra.tpl
@@ -101,7 +101,12 @@ $(function(){
 
         let combinationId = $(this).data('id_combinacion');
         let eanInput = combinationId ? $('#new_combination_' + combinationId + '_ean') : $('#new_product_ean');
-        data.ean = eanInput.val();
+        data.ean = eanInput.val().trim();
+
+        if (!data.ean) {
+            showErrorMessage('El campo EAN no puede estar vacío.');
+            return;
+        }
 
         if (combinationId) {
             data.combinationId = combinationId;
diff --git a/upgrade/upgrade-1.4.php b/upgrade/upgrade-1.4.php
new file mode 100644
index 0000000..b0109cd
--- /dev/null
+++ b/upgrade/upgrade-1.4.php
@@ -0,0 +1,16 @@
+<?php
+
+function upgrade_module_1_4($module) {
+    $sql = array();
+
+    $sql[] = "ALTER TABLE `"._DB_PREFIX_.$module->prefijo."multiean`
+              ADD UNIQUE KEY `unique_ean_per_product_combination` (`id_product`, `ean13`);";
+
+    foreach ($sql as $query) {
+        if (Db::getInstance()->execute($query) == false) {
+            return false;
+        }
+    }
+
+    return true;
+}