--- a/layout/base/nsRefreshDriver.cpp
+++ b/layout/base/nsRefreshDriver.cpp
@@ -2058,17 +2058,17 @@ nsRefreshDriver::WillRefresh(mozilla::Ti
 bool
 nsRefreshDriver::IsWaitingForPaint(mozilla::TimeStamp aTime)
 {
   if (mTestControllingRefreshes) {
     return false;
   }
 
   if (aTime > (mMostRecentTick + TimeDuration::FromMilliseconds(mWarningThreshold * 1000))) {
-    gfxCriticalNote << "Refresh driver waiting for the compositor for"
+    gfxCriticalNote << "Refresh driver waiting for the compositor for "
                     << (aTime - mMostRecentTick).ToSeconds()
                     << " seconds.";
     mWarningThreshold *= 2;
   }
 
   if (mWaitingForTransaction) {
     mSkippedPaints = true;
     return true;