diff --git a/application/itopwebpage.class.inc.php b/application/itopwebpage.class.inc.php
index 9dda44bdf..9cc27ac98 100644
--- a/application/itopwebpage.class.inc.php
+++ b/application/itopwebpage.class.inc.php
@@ -112,9 +112,11 @@ class iTopWebPage extends NiceWebPage implements iTabbedPage
 		$sSearchNbSelected = addslashes(Dict::S('UI:SearchValue:NbSelected'));
 		$this->add_dict_entry('UI:FillAllMandatoryFields');
 
-		$this->add_dict_entries('UI:Search:');
-		$this->add_dict_entries('UI:Button:');
 		$this->add_dict_entries('Error:');
+		$this->add_dict_entries('UI:Button:');
+		$this->add_dict_entries('UI:Search:');
+		$this->add_dict_entry('UI:UndefinedObject');
+		$this->add_dict_entries('Enum:Undefined');
 
 
 		if (!$this->IsPrintableVersion())
diff --git a/js/search/search_form_criteria.js b/js/search/search_form_criteria.js
index 7abb41dcd..fda9b2c3a 100644
--- a/js/search/search_form_criteria.js
+++ b/js/search/search_form_criteria.js
@@ -15,11 +15,11 @@ $(function()
 			'values': [],
 			'oql': '',
 			'is_removable': true, // Not used for now. If we come to show locked criterion they will need to have this flag set to false.
-			'is_null_allowed': false,
 
 			'field': {
 				'label': '',
 				'allowed_values': null,
+				'is_null_allowed': false,
 			},
 			// Available operators. They can be extended or restricted by derivated widgets (see this._initOperators() for more informations)
 			'available_operators': {
diff --git a/js/search/search_form_criteria_enum.js b/js/search/search_form_criteria_enum.js
index eae65f3c1..ead3d7d7f 100644
--- a/js/search/search_form_criteria_enum.js
+++ b/js/search/search_form_criteria_enum.js
@@ -18,7 +18,15 @@ $(function()
 					'code': 'in',
 					'rank': 10,
 				},
-				'=': null,	// Remove this one from enum widget.
+				'=': null,			// Remove this one from enum widget.
+				'empty': null,		// Remove as it will be handle by the "null" value in the "IN" operator
+				'not_empty': null,	// Remove as it will be handle by the "null" value in the "IN" operator
+			},
+
+			// Null value
+			'null_value': {
+				'code': null,
+				'label': Dict.S('Enum:Undefined'),
 			},
 		},
 
@@ -93,6 +101,18 @@ $(function()
 
 			// - Allowed values
 			var oAllowedValuesElem = $('<div class="sfc_opc_mc_items"></div>');
+			//   - Null value is allowed
+			// TODO: We might want to move this into the allowed_values for a standard behavior. But that needs to know how to send the "null" value to the server.
+			if(this.options.field.is_null_allowed === true)
+			{
+				var sItemId = 'value_' + sOpId + '_null';
+				var sValCode = this.options.null_value.code;
+				var sValLabel = this.options.null_value.label;
+				var oValueElem = $('<div class="sfc_opc_mc_item" data-value-code="' + sValCode + '"></div>')
+					.append('<label for="' + sItemId + '"><input type="checkbox" id="' + sItemId + '" value="' + sValCode + '"/>' + sValLabel + '</label>')
+					.appendTo(oAllowedValuesElem);
+			}
+			//   - Regular allowed values
 			if(this.options.field.allowed_values.values !== undefined)
 			{
 				var aSortedValues = this._sortValuesByLabel(this.options.field.allowed_values.values);
diff --git a/js/search/search_form_criteria_external_key.js b/js/search/search_form_criteria_external_key.js
index ff31806be..1513cb24e 100644
--- a/js/search/search_form_criteria_external_key.js
+++ b/js/search/search_form_criteria_external_key.js
@@ -9,6 +9,10 @@ $(function()
 		// default options
 		options:
 		{
+			// Null value
+			'null_value': {
+				'label': Dict.S('UI:UndefinedObject'),
+			}
 		},
 
    
diff --git a/js/search/search_form_handler.js b/js/search/search_form_handler.js
index 48702ea26..d4bcf11f5 100644
--- a/js/search/search_form_handler.js
+++ b/js/search/search_form_handler.js
@@ -446,6 +446,7 @@ $(function()
 						code: oFieldDef.code,
 						widget: oFieldDef.widget,
 						allowed_values: oFieldDef.allowed_values,
+						is_null_allowed: oFieldDef.is_null_allowed,
 					};
 				}