diff --git a/application/utils.inc.php b/application/utils.inc.php
index 581b63089..cdf90877b 100644
--- a/application/utils.inc.php
+++ b/application/utils.inc.php
@@ -464,9 +464,9 @@ class utils
 	{
 		$sSelectionMode = utils::ReadParam('selectionMode', '');
 
-		if ($sSelectionMode === '')
+		if ($sSelectionMode != 'positive' && $sSelectionMode != 'negative')
 		{
-			throw new CoreException('selectionMode is mandatory');
+			throw new CoreException('selectionMode must be either positive or negative');
 		}
 
 		// Paginated selection
diff --git a/js/searchformforeignkeys.js b/js/searchformforeignkeys.js
index da43278a4..6e54ac7c5 100644
--- a/js/searchformforeignkeys.js
+++ b/js/searchformforeignkeys.js
@@ -229,7 +229,7 @@ function SearchFormForeignKeys(id, sTargetClass, sAttCode, oSearchWidgetElmt, sF
 		var selectionMode = $(':input[name="selectionMode"]', context);
 		if (selectionMode.length > 0) {
 			// Paginated table retrieve the mode and the exceptions
-			theMap['selectionMode'] = selectionMode.val();
+			theMap['selectionMode'] = (selectionMode.val() == 'negative') ? 'negative' : 'positive';
 			$('#fs_SearchFormToAdd_'+me.id+' :input').each(function () {
 				theMap[this.name] = this.value;
 			});