diff --git a/src/optimize.cls.php b/src/optimize.cls.php
index 59855f316..3efac11b9 100644
--- a/src/optimize.cls.php
+++ b/src/optimize.cls.php
@@ -1236,6 +1236,7 @@ private function _js_defer( $ori, $src ) {
 		}
 
 		if (strpos($ori, 'defer') !== false) {
+			self::debug2('bypass: attr defer exist');
 			return false;
 		}
 		if (strpos($ori, 'data-deferred') !== false) {