--- a/dom/performance/Performance.cpp
+++ b/dom/performance/Performance.cpp
@@ -234,20 +234,19 @@ Performance::ClearResourceTimings()
 {
   MOZ_ASSERT(NS_IsMainThread());
   mResourceEntries.Clear();
 }
 
 DOMHighResTimeStamp
 Performance::RoundTime(double aTime) const
 {
-  // Round down to the nearest 5us, because if the timer is too accurate people
-  // can do nasty timing attacks with it.  See similar code in the worker
-  // Performance implementation.
-  const double maxResolutionMs = 0.005;
+  // Round down to the nearest 20us, because if the timer is too accurate people
+  // can do nasty timing attacks with it.
+  const double maxResolutionMs = 0.020;
   return nsRFPService::ReduceTimePrecisionAsMSecs(
     floor(aTime / maxResolutionMs) * maxResolutionMs);
 }
 
 
 void
 Performance::Mark(const nsAString& aName, ErrorResult& aRv)
 {