--- a/content/media/GraphDriver.cpp
+++ b/content/media/GraphDriver.cpp
@@ -84,17 +84,17 @@ void GraphDriver::EnsureImmediateWakeUpL
 
 void GraphDriver::UpdateStateComputedTime(GraphTime aStateComputedTime)
 {
   MOZ_ASSERT(aStateComputedTime > mIterationEnd);
   // The next state computed time can be the same as the previous, here: it
   // means the driver would be have been blocking indefinitly, but the graph has
   // been woken up right after having been to sleep.
   if (aStateComputedTime < mStateComputedTime) {
-    printf("State time can't go backward %ld < mStateComputedTime.\n", aStateComputedTime, mStateComputedTime);
+    printf("State time can't go backward %ld < %ld.\n", static_cast<long>(aStateComputedTime), static_cast<long>(mStateComputedTime));
   }
 
   mStateComputedTime = aStateComputedTime;
 }
 
 void GraphDriver::EnsureNextIteration()
 {
   MonitorAutoLock lock(mGraphImpl->GetMonitor());