diff --git a/prototype/UI/index.html b/prototype/UI/index.html
index 841230f12..14d7337aa 100644
--- a/prototype/UI/index.html
+++ b/prototype/UI/index.html
@@ -74,18 +74,21 @@
 
         if (model instanceof Delete) {
             element = document.createElement("div");
+            element.classList.add("patch");
             element.classList.add("delete");
             element.appendChild(toDOM(model.before));
         }
 
         if (model instanceof Insert) {
             element = document.createElement("div");
+            element.classList.add("patch");
             element.classList.add("insert");
             element.appendChild(toDOM(model.after));
         }
 
         if (model instanceof Replace) {
             element = document.createElement("div");
+            element.classList.add("patch");
             element.classList.add("replace");
             var before = toDOM(model.before);
             before.classList.add("delete");