-diff -urN a/libavformat/matroskadec.c b/libavformat/matroskadec.c
---- a/libavformat/matroskadec.c 2019-12-02 08:48:03.116361462 -0700
-+++ b/libavformat/matroskadec.c 2019-12-02 08:52:16.725218816 -0700
-@@ -4224,6 +4224,7 @@
- AVInputFormat ff_matroska_demuxer = {
- .name = "matroska,webm",
- .long_name = NULL_IF_CONFIG_SMALL("Matroska / WebM"),
-+ .flags = AVFMT_SEEK_NOSTREAMS,
- .extensions = "mkv,mk3d,mka,mks",
- .priv_data_size = sizeof(MatroskaDemuxContext),
- .read_probe = matroska_probe,
-@@ -4237,6 +4238,7 @@
- AVInputFormat ff_webm_dash_manifest_demuxer = {
+--- a/libavformat/matroskadec.c
++++ b/libavformat/matroskadec.c
+@@ -4432,6 +4432,7 @@
+ const AVInputFormat ff_webm_dash_manifest_demuxer = {