diff -u b/core/lib/Drupal/Core/Entity/Query/QueryBase.php b/core/lib/Drupal/Core/Entity/Query/QueryBase.php
--- b/core/lib/Drupal/Core/Entity/Query/QueryBase.php
+++ b/core/lib/Drupal/Core/Entity/Query/QueryBase.php
@@ -430,7 +430,7 @@
    */
   public static function getNamespace($object) {
     $class = get_class($object);
-    return substr($class, 0, strrpos($class, '\\') + 1);
+    return substr($class, 0, strrpos($class, '\\'));
   }
 
 }