diff --git a/XMLHttpRequest/progress-events-response-data-gzip.htm b/XMLHttpRequest/progress-events-response-data-gzip.htm
index dc166a2..0580646 100644
--- a/XMLHttpRequest/progress-events-response-data-gzip.htm
+++ b/XMLHttpRequest/progress-events-response-data-gzip.htm
@@ -36,17 +36,20 @@

           * If lengthComputable is true:
               * Event.total must match Content-length header
-              * event.loaded should be a smaller number while resource is loading
-                and match Content-length when loading is finished
-              * Setting event.loaded to equal event.total for each progress event if the
-                resource is not fully downloaded would be cheating
+              * event.loaded must only ever increase in progress events
+                (and may never repeat its value).
+              * event.loaded must never exceed the Content-length.

           * If lengthComputable is false:
               * event.total should be 0
+              * event.loaded must only ever increase in progress events
+                (and may never repeat its value).
               * event.loaded should be the length of the decompressed content, i.e.
                 bigger than Content-length header value when finished loading

         */
+        var lastTotal;
+        var lastLoaded = -1;
         client.addEventListener('loadend', test.step_func(function(e){
           var len = parseInt(client.getResponseHeader('content-length'), 10)
           if(e.lengthComputable){
@@ -59,14 +62,17 @@
           test.done();
         }), false)
         client.addEventListener('progress', test.step_func(function(e){
-          if(e.lengthComputable && e.total && e.loaded && e.target.readyState < 4){
-            assert_not_equals(e.total, e.loaded, 'total should not equal loaded while download/decode is incomplete')
-            // We should only do this assertation once
-            // it's theoretically possible that all the data would get in
-            // and a progress event fire before the readyState switches from 3 to 4 -
-            // in this case we might report bogus and random failures. Better to remove the event listener again..
-            client.removeEventListener('progress', arguments.callee, false);
+          if(lastTotal === undefined){
+            lastTotal = e.total;
           }
+          if(e.lengthComputable && e.total && e.loaded){
+            assert_equals(e.total, lastTotal, 'event.total should remain invariant')
+            assert_less_than_equal(e.loaded, lastTotal, 'event.loaded should not exceed content-length')
+          }else{
+            assert_equals(e.total, 0, 'event.total should be 0')
+          }
+          assert_greater_than(e.loaded, lastLoaded, 'event.loaded should only ever increase')
+          lastLoaded = e.loaded;
         }), false)
         // image.gif is 165375 bytes compressed. Sending 45000 bytes at a time with 1 second delay will load it in 4 seconds
         client.open("GET", "resources/image.gif?pipe=gzip|trickle(45000:d1:r2)", true)