diff --git a/dom/media/fmp4/PlatformDecoderModule.cpp b/dom/media/fmp4/PlatformDecoderModule.cpp
index 4f57b068bf..3583e228d2 100644
--- a/dom/media/fmp4/PlatformDecoderModule.cpp
+++ b/dom/media/fmp4/PlatformDecoderModule.cpp
@@ -151,26 +151,26 @@ PlatformDecoderModule::CreateDecoder(const TrackInfo& aConfig,
 {
   nsRefPtr<MediaDataDecoder> m;
 
-  if (aConfig.IsAudio()) {
-    m = CreateAudioDecoder(static_cast<const AudioInfo&>(aConfig),
+  if (aConfig.GetAsAudioInfo()) {
+    m = CreateAudioDecoder(*aConfig.GetAsAudioInfo(),
                            aTaskQueue,
                            aCallback);
     return m.forget();
   }
 
-  if (!aConfig.IsVideo()) {
+  if (!aConfig.GetAsVideoInfo()) {
     return nullptr;
   }
 
   if (H264Converter::IsH264(aConfig)) {
     m = new H264Converter(this,
-                          static_cast<const VideoInfo&>(aConfig),
+                          *aConfig.GetAsVideoInfo(),
                           aLayersBackend,
                           aImageContainer,
                           aTaskQueue,
                           aCallback);
   } else {
-    m = CreateVideoDecoder(static_cast<const VideoInfo&>(aConfig),
+    m = CreateVideoDecoder(*aConfig.GetAsVideoInfo(),
                            aLayersBackend,
                            aImageContainer,
                            aTaskQueue,