diff --git a/core/oqlclassnode.class.inc.php b/core/oqlclassnode.class.inc.php
index da157f588..3c078ab14 100644
--- a/core/oqlclassnode.class.inc.php
+++ b/core/oqlclassnode.class.inc.php
@@ -331,4 +331,12 @@ class OQLJoin
 		return $this->sRightField;
 	}
 
+	/**
+	 * @return string
+	 */
+	public function GetLeftField()
+	{
+		return $this->sLeftField;
+	}
+
 }
diff --git a/core/oqlclasstreebuilder.class.inc.php b/core/oqlclasstreebuilder.class.inc.php
index 2e25fb1dd..a397ab3db 100644
--- a/core/oqlclasstreebuilder.class.inc.php
+++ b/core/oqlclasstreebuilder.class.inc.php
@@ -294,13 +294,6 @@ class OQLClassTreeBuilder
 								$oClassExpr = new FieldExpression($sClassAttCode, $this->sClassAlias);
 								$oClassRestriction = new BinaryExpression($oClassExpr, 'IN', $oClassListExpr);
 								$oQBContextExpressions->AddCondition($oClassRestriction);
-							} elseif (($oKeyAttDef instanceof AttributeExternalKey) && $sKeyClass != $oKeyAttDef->GetTargetClass()) {
-								$sClassAttCode = 'finalclass';
-								$oClassListExpr = ListExpression::FromScalars(MetaModel::EnumChildClasses($sKeyClass,
-									ENUM_CHILD_CLASSES_ALL));
-								$oClassExpr = new FieldExpression($sClassAttCode, $sKeyClassAlias);
-								$oClassRestriction = new BinaryExpression($oClassExpr, 'IN', $oClassListExpr);
-								$oQBContextExpressions->AddCondition($oClassRestriction);
 							}
 
 							// Translate prior to recursing
diff --git a/core/oqlclasstreeoptimizer.class.inc.php b/core/oqlclasstreeoptimizer.class.inc.php
index 0472863e7..1e12384e9 100644
--- a/core/oqlclasstreeoptimizer.class.inc.php
+++ b/core/oqlclasstreeoptimizer.class.inc.php
@@ -50,8 +50,15 @@ class OQLClassTreeOptimizer
 				{
 					if ($oJoin->IsOutbound())
 					{
-						// The join is not used, remove from tree
-						$oCurrentClassNode->RemoveJoin($sLeftKey, $index);
+						// If joined class in not the same class than the external key target class
+						// then the join cannot be removed because it is used to filter the request
+						$sJoinedClass = $oJoin->GetOOQLClassNode()->GetNodeClass();
+						$sExtKeyAttCode = $oJoin->GetLeftField();
+						$oExtKeyAttDef = MetaModel::GetAttributeDef($oCurrentClassNode->GetNodeClass(), $sExtKeyAttCode);
+						if ($sJoinedClass == $oExtKeyAttDef->GetTargetClass()) {
+							// The join is not used, remove from tree
+							$oCurrentClassNode->RemoveJoin($sLeftKey, $index);
+						}
 					}
 					else
 					{
diff --git a/test/core/OQLTest.php b/test/core/OQLTest.php
index d419f46b3..54b0293d7 100644
--- a/test/core/OQLTest.php
+++ b/test/core/OQLTest.php
@@ -441,8 +441,8 @@ class OQLTest extends ItopDataTestCase
 				"SELECT `U` FROM `UserRequest` AS `U`
     INNER JOIN `lnkContactToTicket` AS `l`
       ON `U`.`id` = `l`.`ticket_id` 
-        INNER JOIN `Contact` AS `T_Contact`
-          ON `l`.`contact_id` = `T_Contact`.`id`",
+        INNER JOIN `Team` AS `T`
+          ON `l`.`contact_id` = `T`.`id`",
 			],
 			'Bug 3660 2' => [
 				"SELECT UserRequest AS U