--- a/dom/media/webaudio/WaveShaperNode.cpp
+++ b/dom/media/webaudio/WaveShaperNode.cpp
@@ -257,17 +257,17 @@ public:
               static_cast<const float*>(aInput.mChannelData[i]),
                                         aInput.mVolume,
                                         alignedScaledInput);
           inputSamples = alignedScaledInput;
         } else {
           inputSamples = static_cast<const float*>(aInput.mChannelData[i]);
         }
       } else {
-        PodZero(alignedScaledInput);
+        PodZero(alignedScaledInput, WEBAUDIO_BLOCK_SIZE);
         inputSamples = alignedScaledInput;
       }
       float* outputBuffer = aOutput->ChannelFloatsForWrite(i);
       float* sampleBuffer;
 
       switch (mType) {
       case OverSampleType::None:
         mResampler.Reset(channelCount, aStream->SampleRate(), OverSampleType::None);

--- a/dom/media/webaudio/test/test_waveShaperGain.html
+++ b/dom/media/webaudio/test/test_waveShaperGain.html
@@ -50,18 +50,19 @@ context.startRendering().then(buffer => 
 
   oscillator.start(0);
   oscillator.connect(gain);
 
   // to silence
   gain.gain.value = 0;
   gain.connect(waveShaper);
 
-  // convert all signal into 1.0
-  waveShaper.curve = new Float32Array([ 1, 1 ]);
+  // convert all signal into 1.0. The non unity values are to detect the use
+  // of uninitialized buffers (see Bug 1283910).
+  waveShaper.curve = new Float32Array([ 0.5, 0.5, 0.5, 0.5, 0.5, 1, 1, 0.5, 0.5, 0.5, 0.5, 0.5 ]);
   waveShaper.connect(context.destination);
 
   context.startRendering().then((buffer) => {
     var result = buffer.getChannelData(0);
     ok(result.every(x => x === 1), "WaveShaper handles zero gain properly");
     SimpleTest.finish();
   });
 });