diff --git a/xhr.bs b/xhr.bs
index 7fea6a8..ba4fc2a 100644
--- a/xhr.bs
+++ b/xhr.bs
@@ -1753,14 +1753,14 @@ interface ProgressEvent : Event {
   constructor(DOMString type, optional ProgressEventInit eventInitDict = {});
 
   readonly attribute boolean lengthComputable;
-  readonly attribute unsigned long long loaded;
-  readonly attribute unsigned long long total;
+  readonly attribute double loaded;
+  readonly attribute double total;
 };
 
 dictionary ProgressEventInit : EventInit {
   boolean lengthComputable = false;
-  unsigned long long loaded = 0;
-  unsigned long long total = 0;
+  double loaded = 0;
+  double total = 0;
 };
 </pre>