diff --git a/dom/media/webaudio/OscillatorNode.cpp b/dom/media/webaudio/OscillatorNode.cpp
--- a/dom/media/webaudio/OscillatorNode.cpp
+++ b/dom/media/webaudio/OscillatorNode.cpp
@@ -298,17 +298,17 @@ public:
     }
 
     if (ticks >= mStop) {
       // We've finished playing.
       ComputeSilence(aOutput);
       *aFinished = true;
       return;
     }
-    if (ticks + WEBAUDIO_BLOCK_SIZE < mStart) {
+    if (ticks + WEBAUDIO_BLOCK_SIZE <= mStart) {
       // We're not playing yet.
       ComputeSilence(aOutput);
       return;
     }
 
     AllocateAudioBlock(1, aOutput);
     float* output = static_cast<float*>(
         const_cast<void*>(aOutput->mChannelData[0]));
