diff --git src/wp-includes/js/shortcode.js src/wp-includes/js/shortcode.js
index 7028f6a..cd37392 100644
--- src/wp-includes/js/shortcode.js
+++ src/wp-includes/js/shortcode.js
@@ -327,7 +327,7 @@ window.wp = window.wp || {};
 				text += ' ' + attr;
 
 				// Use empty attribute notation where possible.
-				if ( '' === value ) {
+				if ( '' === value && 'alt' !== attr ) {
 					return;
 				}