diff --git a/core/oql/expression.class.inc.php b/core/oql/expression.class.inc.php
index 98510a594..c6ab22fb4 100644
--- a/core/oql/expression.class.inc.php
+++ b/core/oql/expression.class.inc.php
@@ -1602,6 +1602,7 @@ class FunctionExpression extends Expression
 				{
 					$aCriteria = array_merge($oExpression->GetCriterion($oSearch, $aArgs, $bRetrofitParams, $oAttDef), $aCriteria);
 				}
+				$aCriteria['has_undefined'] = true;
 				break;
 
 			case 'NOW':
diff --git a/dictionaries/fr.dictionary.itop.ui.php b/dictionaries/fr.dictionary.itop.ui.php
index fadf34b1a..68763f5af 100644
--- a/dictionaries/fr.dictionary.itop.ui.php
+++ b/dictionaries/fr.dictionary.itop.ui.php
@@ -1241,8 +1241,8 @@ Lors de l\'association à un déclencheur, on attribue à chaque action un numé
 // Expression to Natural language
 //
 Dict::Add('FR FR', 'French', 'Français', array(
-	'Expression:Operator:AND' => 'ET',
-	'Expression:Operator:OR' => 'OU',
+	'Expression:Operator:AND' => ' ET ',
+	'Expression:Operator:OR' => ' OU ',
 	'Expression:Unit:Short:DAY' => 'j',
 	'Expression:Unit:Short:WEEK' => 's',
 	'Expression:Unit:Short:MONTH' => 'm',
diff --git a/sources/application/search/criterionconversion/criteriontosearchform.class.inc.php b/sources/application/search/criterionconversion/criteriontosearchform.class.inc.php
index ac3eed301..4970a7a2e 100644
--- a/sources/application/search/criterionconversion/criteriontosearchform.class.inc.php
+++ b/sources/application/search/criterionconversion/criteriontosearchform.class.inc.php
@@ -334,11 +334,6 @@ class CriterionToSearchForm extends CriterionConversionAbstract
 		return $aCriteria;
 	}
 
-	protected static function EnumToSearchForm($aCriteria, $aFields)
-	{
-		return self::ExternalKeyToSearchForm($aCriteria, $aFields);
-	}
-
 	protected static function DateToSearchForm($aCriteria, $aFields)
 	{
 		return self::DateTimeToSearchForm($aCriteria, $aFields);
@@ -417,6 +412,10 @@ class CriterionToSearchForm extends CriterionConversionAbstract
 		return $aCriteria;
 	}
 
+	protected static function EnumToSearchForm($aCriteria, $aFields)
+	{
+		return self::ExternalKeyToSearchForm($aCriteria, $aFields);
+	}
 
 	protected static function ExternalKeyToSearchForm($aCriteria, $aFields)
 	{
@@ -442,6 +441,14 @@ class CriterionToSearchForm extends CriterionConversionAbstract
 				break;
 			case 'IN':
 				break;
+			case 'OR':
+				// Special case when undefined and other values are selected
+				$aCriteria['operator'] = CriterionConversionAbstract::OP_IN;
+				if (isset($aCriteria['has_undefined']) && $aCriteria['has_undefined'])
+				{
+					$aCriteria['values'][] = array('value' => 'null', 'label' => 'null');
+				}
+				break;
 			default:
 				// Unknown operator
 				$aCriteria['widget'] = AttributeDefinition::SEARCH_WIDGET_TYPE_RAW;
diff --git a/test/application/search/CriterionConversionTest.php b/test/application/search/CriterionConversionTest.php
index aff5eea85..98da18c5f 100644
--- a/test/application/search/CriterionConversionTest.php
+++ b/test/application/search/CriterionConversionTest.php
@@ -355,6 +355,7 @@ class CriterionConversionTest extends ItopDataTestCase
 			'enum IN' => array('OQL' => "SELECT Contact WHERE status IN ('active', 'inactive')"),
 			'enum NOT IN' => array('OQL' => "SELECT Contact WHERE status NOT IN ('active')"),
 			'enum undefined' => array('OQL' => "SELECT FunctionalCI WHERE ((business_criticity = 'high') OR ISNULL(business_criticity)) AND 1"),
+			'enum undefined1' => array('OQL' => "SELECT FunctionalCI WHERE ((business_criticity IN ('high', 'medium')) OR ISNULL(business_criticity)) AND 1"),
 			'key NOT IN' => array('OQL' => "SELECT Contact WHERE org_id NOT IN ('1')"),
 			'key IN' => array('OQL' => "SELECT Contact WHERE org_id IN ('1')"),
 			'key empty' => array('OQL' => "SELECT Person WHERE location_id = '0'"),
diff --git a/test/application/search/SearchFormTest.php b/test/application/search/SearchFormTest.php
index 21aaec5e9..f2b538bdb 100644
--- a/test/application/search/SearchFormTest.php
+++ b/test/application/search/SearchFormTest.php
@@ -56,9 +56,9 @@ class SearchFormTest extends ItopDataTestCase
 	public function GetFieldsProvider()
 	{
 		return array(
-			array("SELECT Contact", 7, 'zlist'),
+			array("SELECT Contact", 8, 'zlist'),
 			array("SELECT Contact AS C WHERE C.status = 'active'", 4, 'others'),
-			array("SELECT Person", 11, 'zlist'),
+			array("SELECT Person", 12, 'zlist'),
 		);
 	}