diff --git a/core/attributedef.class.inc.php b/core/attributedef.class.inc.php
index 999fe3aa8..bf357db51 100644
--- a/core/attributedef.class.inc.php
+++ b/core/attributedef.class.inc.php
@@ -13245,27 +13245,11 @@ class AttributeCustomFields extends AttributeDefinition
 	 */
 	public function CheckValue(DBObject $oHostObject, $value)
 	{
-		try
-		{
+		try {
 			$oHandler = $this->GetHandler($value->GetValues());
 			$oHandler->BuildForm($oHostObject, '');
-			$oForm = $oHandler->GetForm();
-			$oForm->Validate();
-			if ($oForm->GetValid())
-			{
-				$ret = true;
-			}
-			else
-			{
-				$aMessages = array();
-				foreach($oForm->GetErrorMessages() as $sFieldId => $aFieldMessages)
-				{
-					$aMessages[] = $sFieldId.': '.implode(', ', $aFieldMessages);
-				}
-				$ret = 'Invalid value: '.implode(', ', $aMessages);
-			}
-		} catch (Exception $e)
-		{
+			$ret = $oHandler->Validate($oHostObject);
+		} catch (Exception $e) {
 			$ret = $e->getMessage();
 		}
 
diff --git a/core/customfieldshandler.class.inc.php b/core/customfieldshandler.class.inc.php
index dac4f6c7d..826172ae3 100644
--- a/core/customfieldshandler.class.inc.php
+++ b/core/customfieldshandler.class.inc.php
@@ -47,20 +47,47 @@ abstract class CustomFieldsHandler {
 	 *
 	 * @param $sAttCode
 	 */
-	final public function __construct($sAttCode)
-	{
+	final public function __construct($sAttCode) {
 		$this->sAttCode = $sAttCode;
 		$this->aValues = null;
 	}
 
 	abstract public function BuildForm(DBObject $oHostObject, $sFormId);
 
+	/**
+	 * @returns true|string true if no error found, error message otherwise
+	 * @throws \ApplicationException if {@link static::$oForm} attribute not initialized yet
+	 * @since 3.1.0 N°6322 N°1150 Add template_id checks
+	 */
+	public function Validate(DBObject $oHostObject) {
+		if (false === isset($this->oForm)) {
+			throw new ApplicationException('oForm attribute not init yet. You must call BuildForm before this method !');
+		}
+
+		try {
+			$this->oForm->Validate();
+			if ($this->oForm->GetValid()) {
+				$ret = true;
+			}
+			else {
+				$aMessages = array();
+				foreach ($this->oForm->GetErrorMessages() as $sFieldId => $aFieldMessages) {
+					$aMessages[] = $sFieldId.': '.implode(', ', $aFieldMessages);
+				}
+				$ret = 'Invalid value: '.implode(', ', $aMessages);
+			}
+		} catch (Exception $e) {
+			$ret = $e->getMessage();
+		}
+
+		return $ret;
+	}
+
 	/**
 	 *
 	 * @return \Combodo\iTop\Form\Form
 	 */
-	public function GetForm()
-	{
+	public function GetForm() {
 		return $this->oForm;
 	}
 
@@ -69,16 +96,14 @@ abstract class CustomFieldsHandler {
 		$this->aValues = $aValues;
 	}
 
-	static public function GetPrerequisiteAttributes($sClass = null)
-	{
+	public static function GetPrerequisiteAttributes($sClass = null) {
 		return array();
 	}
 
 	/**
 	 * List the available verbs for 'GetForTemplate'
 	 */
-	static public function EnumTemplateVerbs()
-	{
+	public static function EnumTemplateVerbs() {
 		return array();
 	}