diff --git a/dblayeroo.php b/dblayeroo.php
index efca24e..c0055b3 100644
--- a/dblayeroo.php
+++ b/dblayeroo.php
@@ -1564,7 +1564,7 @@ class dblayeroo
       $this->DBException ("Invalid joinType provided to join (not known)");
     if (! is_object ($object))
       $this->DBException ("Invalid object provided to join (not object)");
-    if (get_class ($object) !== __CLASS__)
+    if (! is_subclass_of ($object, __CLASS__))
       $this->DBException (
         "Invalid object provided to join (not dblayeroo object)");
     if ($this->dsn !== $object->dsn)