Index: src/wp-includes/js/twemoji.js
===================================================================
--- src/wp-includes/js/twemoji.js	(revision 35626)
+++ src/wp-includes/js/twemoji.js	(working copy)
@@ -89,6 +89,7 @@
        */
       onerror: function onerror() {
         if (this.parentNode) {
+          this.setAttribute( 'data-error', 'load-failed' );
           this.parentNode.replaceChild(createText(this.alt), this);
         }
       },
Index: src/wp-includes/js/wp-emoji.js
===================================================================
--- src/wp-includes/js/wp-emoji.js	(revision 35626)
+++ src/wp-includes/js/wp-emoji.js	(working copy)
@@ -58,7 +58,8 @@
 							ii === 1 && removedNodes.length === 1 &&
 							addedNodes[0].nodeType === 3 &&
 							removedNodes[0].nodeName === 'IMG' &&
-							addedNodes[0].data === removedNodes[0].alt
+							addedNodes[0].data === removedNodes[0].alt &&
+							'load-failed' === removedNodes[0].getAttribute( 'data-error' )
 						) {
 							return;
 						}