--- a/dom/media/GraphDriver.cpp
+++ b/dom/media/GraphDriver.cpp
@@ -621,17 +621,17 @@ AudioCallbackDriver::Init()
         cubeb_stream_init(CubebUtils::GetCubebContext(), &stream,
                           "AudioCallbackDriver",
                           input_id,
                           mGraphImpl->mInputWanted ? &input : nullptr,
                           output_id,
                           mGraphImpl->mOutputWanted ? &output : nullptr, latency,
                           DataCallback_s, StateCallback_s, this) == CUBEB_OK) {
       mAudioStream.own(stream);
-      int rv = cubeb_stream_set_volume(mAudioStream, CubebUtils::GetVolumeScale());
+      DebugOnly<int> rv = cubeb_stream_set_volume(mAudioStream, CubebUtils::GetVolumeScale());
       NS_WARN_IF_FALSE(rv == CUBEB_OK,
           "Could not set the audio stream volume in GraphDriver.cpp");
     } else {
 #ifdef MOZ_WEBRTC
       StaticMutexAutoUnlock unlock(AudioInputCubeb::Mutex());
 #endif
       NS_WARNING("Could not create a cubeb stream for MediaStreamGraph, falling back to a SystemClockDriver");
       // Fall back to a driver using a normal thread.