diff --git a/prototype/UI/index.html b/prototype/UI/index.html
index f52896a9e..0302dd157 100644
--- a/prototype/UI/index.html
+++ b/prototype/UI/index.html
@@ -226,7 +226,7 @@
     function Diff(json, a, b) {
         if (json.pure != null) { this.pure = patch(json.pure, a, b); }
         if (json.roll != null) {
-            this.ranges = json.extract;
+            this.ranges = json.roll.extract;
             this.sources = [ a, b ];
             this.roll = syntax(json.roll.unwrap, function(x) { return new Diff(x, a, b); });
         }