--- a/dom/media/MediaInfo.h
+++ b/dom/media/MediaInfo.h
@@ -498,16 +498,17 @@ public:
     ChannelLayout()
       : mChannelMap(0)
       , mValid(false)
     {}
     explicit ChannelLayout(uint32_t aChannels)
       : ChannelLayout(aChannels, SMPTEDefault(aChannels))
     {}
     ChannelLayout(uint32_t aChannels, const Channel* aConfig)
+      : ChannelLayout()
     {
       if (!aConfig) {
         mValid = false;
         return;
       }
       mChannels.AppendElements(aConfig, aChannels);
       UpdateChannelMap();
     }