--- a/content/html/content/src/nsHTMLMediaElement.cpp
+++ b/content/html/content/src/nsHTMLMediaElement.cpp
@@ -3504,22 +3504,24 @@ NS_IMETHODIMP nsHTMLMediaElement::GetPla
 NS_IMETHODIMP nsHTMLMediaElement::SetPlaybackRate(double aPlaybackRate)
 {
   if (aPlaybackRate < 0) {
     return NS_ERROR_NOT_IMPLEMENTED;
   }
 
   mPlaybackRate = ClampPlaybackRate(aPlaybackRate);
 
-  if (mPlaybackRate < 0 ||
-      mPlaybackRate > THRESHOLD_HIGH_PLAYBACKRATE_AUDIO ||
-      mPlaybackRate < THRESHOLD_LOW_PLAYBACKRATE_AUDIO) {
-    SetMutedInternal(true);
-  } else {
-    SetMutedInternal(false);
+  if (!mMuted) {
+    if (mPlaybackRate < 0 ||
+        mPlaybackRate > THRESHOLD_HIGH_PLAYBACKRATE_AUDIO ||
+        mPlaybackRate < THRESHOLD_LOW_PLAYBACKRATE_AUDIO) {
+      SetMutedInternal(true);
+    } else {
+      SetMutedInternal(false);
+    }
   }
 
   if (mDecoder) {
     mDecoder->SetPlaybackRate(mPlaybackRate);
   }
   DispatchAsyncEvent(NS_LITERAL_STRING("ratechange"));
   return NS_OK;
 }