--- a/dom/media/MediaDecoder.cpp
+++ b/dom/media/MediaDecoder.cpp
@@ -634,18 +634,18 @@ MediaDecoder::EnsureTelemetryReported()
       && !mInfo->mAudio.GetAsAudioInfo()->mMimeType.IsEmpty()) {
     codecs.AppendElement(mInfo->mAudio.GetAsAudioInfo()->mMimeType);
   }
   if (mInfo->HasVideo()
       && !mInfo->mVideo.GetAsVideoInfo()->mMimeType.IsEmpty()) {
     codecs.AppendElement(mInfo->mVideo.GetAsVideoInfo()->mMimeType);
   }
   if (codecs.IsEmpty()) {
-    codecs.AppendElement(nsPrintfCString(
-      "resource; %s", mResource->GetContentType().OriginalString().Data()));
+    codecs.AppendElement(
+      nsPrintfCString("resource; %s", ContainerType().OriginalString().Data()));
   }
   for (const nsCString& codec : codecs) {
     LOG("Telemetry MEDIA_CODEC_USED= '%s'", codec.get());
     Telemetry::Accumulate(Telemetry::HistogramID::MEDIA_CODEC_USED, codec);
   }
 
   mTelemetryReported = true;
 }