diff --git a/lib/util/stream_utils.js b/lib/util/stream_utils.js
index 010e015c69..7eb23edbd7 100644
--- a/lib/util/stream_utils.js
+++ b/lib/util/stream_utils.js
@@ -1397,8 +1397,6 @@ shaka.util.StreamUtils = class {
    * @return {shaka.extern.Track}
    */
   static html5TextTrackToTrack(textTrack) {
-    const CLOSED_CAPTION_MIMETYPE =
-        shaka.util.MimeUtils.CEA608_CLOSED_CAPTION_MIMETYPE;
     const StreamUtils = shaka.util.StreamUtils;
 
     /** @type {shaka.extern.Track} */
@@ -1407,7 +1405,8 @@ shaka.util.StreamUtils = class {
     track.type = 'text';
     track.originalTextId = textTrack.id;
     if (textTrack.kind == 'captions') {
-      track.mimeType = CLOSED_CAPTION_MIMETYPE;
+      // See: https://github.com/shaka-project/shaka-player/issues/6233
+      track.mimeType = 'unknown';
     }
     if (textTrack.kind == 'subtitles') {
       track.mimeType = 'text/vtt';