diff --git a/sources/application/search/criterionconversion/criteriontooql.class.inc.php b/sources/application/search/criterionconversion/criteriontooql.class.inc.php
index 4dfc681926..1b43e52f69 100644
--- a/sources/application/search/criterionconversion/criteriontooql.class.inc.php
+++ b/sources/application/search/criterionconversion/criteriontooql.class.inc.php
@@ -129,6 +129,11 @@ class CriterionToOQL extends CriterionConversionAbstract
 		$sClass = $aCriteria['class'];
 		$aValues = $aCriteria['values'];
 
+		if (count($aValues) == 0)
+		{
+			return "({$sRef}  = '')";
+		}
+
 		try
 		{
 			$aAttributeDefs = \MetaModel::ListAttributeDefs($sClass);
@@ -163,6 +168,11 @@ class CriterionToOQL extends CriterionConversionAbstract
 		}
 		$sInList = implode(',', $aInValues);
 
+		if (count($aInValues) == 1)
+		{
+			return "({$sRef} = '$sInList')";
+		}
+
 		return "({$sRef} IN ($sInList))";
 	}