diff --git a/inc/rest.php b/inc/rest.php
index fd5363d6..38cbaf4e 100644
--- a/inc/rest.php
+++ b/inc/rest.php
@@ -718,7 +718,7 @@ public function poll_optimized_images( WP_REST_Request $request ) {
 		foreach ( $final_images as $index => $value ) {
 			$final_images[ $index ]['url'] = Optml_Media_Offload::instance()->get_media_optimized_url(
 				$value['url'],
-				$value['key'],
+				strtolower( $value['key'] ),
 				140,
 				140,
 				[