diff --git a/src/Service.php b/src/Service.php
index d621bee..09c334b 100644
--- a/src/Service.php
+++ b/src/Service.php
@@ -542,7 +542,7 @@ public function buildFilterEntryObject($filterEntry) {
      * @return array
      */
     public function doFilter($classId, array $filters, $fullTextQuery, $from = null, $size = null) {
-        $classDefinition = \Pimcore\Model\Object\ClassDefinition::getById($classId);
+        $classDefinition = \Pimcore\Model\DataObject\ClassDefinition::getById($classId);
 
         $search = $this->getFilter($classDefinition, $filters);