diff --git a/application/cmdbabstract.class.inc.php b/application/cmdbabstract.class.inc.php
index ac220dce1..085a6e6ce 100644
--- a/application/cmdbabstract.class.inc.php
+++ b/application/cmdbabstract.class.inc.php
@@ -1762,7 +1762,12 @@ EOF
 			$sValidationSpan = "<span class=\"form_validation\" id=\"v_{$iId}\"></span>";
 			$sReloadSpan = "<span class=\"field_status\" id=\"fstatus_{$iId}\"></span>";
 			$sHelpText = htmlentities($oAttDef->GetHelpOnEdition(), ENT_QUOTES, 'UTF-8');
-			$aEventsList = array();
+
+			// mandatory field control vars
+			$aEventsList = array(); // contains any native event (like change), plus 'validate' for the form submission
+			$sNullValue = $oAttDef->GetNullValue(); // used for the ValidateField() call in js/forms-json-utils.js
+			$sFieldToValidateId = $iId; // can be different than the displayed field (for example in TagSet)
+
 			switch ($oAttDef->GetEditClass())
 			{
 				case 'Date':
@@ -2139,9 +2144,19 @@ EOF
 					$sJson = $oAttDef->GetJsonForWidget($value, $aArgs);
 					$sEscapedJson = htmlentities($sJson, ENT_QUOTES, 'UTF-8');
 					$sSetInputName = "attr_{$sFormPrefix}{$sAttCode}";
+
+					// handle form validation
+					$aEventsList[] = 'change';
+					$aEventsList[] = 'validate';
+					$sNullValue = '';
+					$sFieldToValidateId = $sFieldToValidateId.AttributeSet::EDITABLE_INPUT_ID_SUFFIX;
+
+					// generate form HTML output
+					$sValidationSpan = "<span class=\"form_validation\" id=\"v_{$sFieldToValidateId}\"></span>";
 					$sHTMLValue = '<div class="field_input_zone field_input_set"><input id="'.$iId.'" name="'.$sSetInputName.'" type="hidden" value="'.$sEscapedJson.'"></div>'.$sValidationSpan.$sReloadSpan;
-					$sScript = "$('#$iId').set_widget();";
+					$sScript = "$('#$iId').set_widget({inputWidgetIdSuffix: '".AttributeSet::EDITABLE_INPUT_ID_SUFFIX."'});";
 					$oPage->add_ready_script($sScript);
+
 					break;
 
 				case 'String':
@@ -2226,14 +2241,13 @@ EOF
 			$sPattern = addslashes($oAttDef->GetValidationPattern()); //'^([0-9]+)$';			
 			if (!empty($aEventsList))
 			{
-				$sNullValue = $oAttDef->GetNullValue();
 				if (!is_numeric($sNullValue))
 				{
 					$sNullValue = "'$sNullValue'"; // Add quotes to turn this into a JS string if it's not a number
 				}
 				$sOriginalValue = ($iFlags & OPT_ATT_MUSTCHANGE) ? json_encode($value) : 'undefined';
-				$oPage->add_ready_script("$('#$iId').bind('".implode(' ',
-						$aEventsList)."', function(evt, sFormId) { return ValidateField('$iId', '$sPattern', $bMandatory, sFormId, $sNullValue, $sOriginalValue) } );\n"); // Bind to a custom event: validate
+				$oPage->add_ready_script("$('#$sFieldToValidateId').bind('".implode(' ',
+						$aEventsList)."', function(evt, sFormId) { return ValidateField('$sFieldToValidateId', '$sPattern', $bMandatory, sFormId, $sNullValue, $sOriginalValue) } );\n"); // Bind to a custom event: validate
 			}
 			$aDependencies = MetaModel::GetDependentAttributes($sClass,
 				$sAttCode); // List of attributes that depend on the current one
diff --git a/core/attributedef.class.inc.php b/core/attributedef.class.inc.php
index 7e46743ed..180a9d996 100644
--- a/core/attributedef.class.inc.php
+++ b/core/attributedef.class.inc.php
@@ -8738,6 +8738,7 @@ class AttributePropertySet extends AttributeTable
 abstract class AttributeSet extends AttributeDBFieldVoid
 {
 	const SEARCH_WIDGET_TYPE = self::SEARCH_WIDGET_TYPE_RAW;
+	const EDITABLE_INPUT_ID_SUFFIX = '-setwidget-values'; // used client side, see js/jquery.itop-set-widget.js
 
 	public function __construct($sCode, array $aParams)
 	{
diff --git a/js/forms-json-utils.js b/js/forms-json-utils.js
index d46227957..0e0602119 100644
--- a/js/forms-json-utils.js
+++ b/js/forms-json-utils.js
@@ -147,6 +147,8 @@ function CheckFields(sFormId, bDisplayAlert)
 	oFormErrors['input_'+sFormId] = null;	// First 'input' with an error, to set the focus to it
 	$('#'+sFormId+' :input').each( function()
 	{
+		// this is synchronous !
+		// each field should register this event to launch ValidateField() if needed
 		validateEventResult = $(this).trigger('validate', sFormId);
 	}
 	);
@@ -210,6 +212,18 @@ function ReportFieldValidationStatus(sFieldId, sFormId, bValid, sExplain)
 	}
 }
 
+/**
+ * To be launched on each field from normal event (click, change, ...) and 'validate' event for form submission.
+ * Calls ReportFieldValidationStatus() to update global vars containing fields status
+ * @param sFieldId
+ * @param sPattern
+ * @param bMandatory
+ * @param sFormId
+ * @param nullValue
+ * @param originalValue
+ * @returns {boolean}
+ * @constructor
+ */
 function ValidateField(sFieldId, sPattern, bMandatory, sFormId, nullValue, originalValue)
 {
 	var bValid = true;
diff --git a/js/jquery.itop-set-widget.js b/js/jquery.itop-set-widget.js
index 27bf5bd44..145cf3fec 100644
--- a/js/jquery.itop-set-widget.js
+++ b/js/jquery.itop-set-widget.js
@@ -62,7 +62,10 @@
 $.widget('itop.set_widget',
 	{
 		// default options
-		options: {isDebug: false},
+		options: {
+			isDebug: false,
+			inputWidgetIdSuffix: "-setwidget-values"
+		},
 
 		PARENT_CSS_CLASS: "attribute-set",
 		ITEM_CSS_CLASS: "attribute-set-item",
@@ -123,7 +126,7 @@ $.widget('itop.set_widget',
 		_generateSelectionWidget: function ($widgetElement) {
 			var $parentElement = $widgetElement.parent(),
 				isWidgetElementDisabled = $widgetElement.prop("disabled"),
-				inputId = $widgetElement.attr("id") + "-setwidget-values";
+				inputId = $widgetElement.attr("id") + this.options.inputWidgetIdSuffix;
 
 			$parentElement.append("<input id='" + inputId + "' value='" + this.originalValue.join(" ") + "'>");
 			var $inputWidget = $("#" + inputId);