--- a/dom/media/webaudio/ConstantSourceNode.cpp
+++ b/dom/media/webaudio/ConstantSourceNode.cpp
@@ -205,17 +205,17 @@ ConstantSourceNode::DestroyMediaStream()
   }
   AudioNode::DestroyMediaStream();
 }
 
 void
 ConstantSourceNode::Start(double aWhen, ErrorResult& aRv)
 {
   if (!WebAudioUtils::IsTimeValid(aWhen)) {
-    aRv.Throw(NS_ERROR_DOM_NOT_SUPPORTED_ERR);
+    aRv.Throw(NS_ERROR_RANGE_ERR);
     return;
   }
 
   if (mStartCalled) {
     aRv.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
     return;
   }
   mStartCalled = true;
@@ -229,17 +229,17 @@ ConstantSourceNode::Start(double aWhen, 
 
   MarkActive();
 }
 
 void
 ConstantSourceNode::Stop(double aWhen, ErrorResult& aRv)
 {
   if (!WebAudioUtils::IsTimeValid(aWhen)) {
-    aRv.Throw(NS_ERROR_DOM_NOT_SUPPORTED_ERR);
+    aRv.Throw(NS_ERROR_RANGE_ERR);
     return;
   }
 
   if (!mStartCalled) {
     aRv.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
     return;
   }