diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index e6631097b8..95189525e3 100644
--- a/libavformat/matroskadec.c
+++ b/libavformat/matroskadec.c
@@ -2390,6 +2390,10 @@ static int matroska_parse_tracks(AVFormatContext *s)
                 return ret;
         } else if (codec_id == AV_CODEC_ID_PRORES && track->codec_priv.size == 4) {
             fourcc = AV_RL32(track->codec_priv.data);
+        } else if (codec_id == AV_CODEC_ID_VP9 && track->codec_priv.size) {
+            /* we don't need any value stored in CodecPrivate.
+               make sure that it's not exported as extradata. */
+            track->codec_priv.size = 0;
         }
         track->codec_priv.size -= extradata_offset;