diff --git src/wp-includes/media.php src/wp-includes/media.php
index f6c5f0f..e7dca8d 100644
--- src/wp-includes/media.php
+++ src/wp-includes/media.php
@@ -3143,8 +3143,10 @@ function wp_prepare_attachment_for_js( $attachment ) {
 
 			/** This filter is documented in wp-includes/media.php */
 			if ( $downsize = apply_filters( 'image_downsize', false, $attachment->ID, $size ) ) {
-				if ( ! $downsize[3] )
+				if ( empty( $downsize[3] ) ) {
 					continue;
+				}
+
 				$sizes[ $size ] = array(
 					'height'      => $downsize[2],
 					'width'       => $downsize[1],