--- a/dom/media/mediasource/MediaSource.cpp
+++ b/dom/media/mediasource/MediaSource.cpp
@@ -110,16 +110,18 @@ MediaSource::IsTypeSupported(const nsASt
       mimeType == MEDIAMIMETYPE("audio/mp4")) {
     if (!Preferences::GetBool("media.mediasource.mp4.enabled", false)) {
       return NS_ERROR_DOM_NOT_SUPPORTED_ERR;
     }
     return NS_OK;
   }
   if (mimeType == MEDIAMIMETYPE("video/webm")) {
     if (!(Preferences::GetBool("media.mediasource.webm.enabled", false) ||
+          containerType->ExtendedType().Codecs().Contains(
+            NS_LITERAL_STRING("vp8")) ||
           IsWebMForced(aDiagnostics))) {
       return NS_ERROR_DOM_NOT_SUPPORTED_ERR;
     }
     return NS_OK;
   }
   if (mimeType == MEDIAMIMETYPE("audio/webm")) {
     if (!(Preferences::GetBool("media.mediasource.webm.enabled", false) ||
           Preferences::GetBool("media.mediasource.webm.audio.enabled", true))) {