-diff -urN a/libavformat/matroskadec.c b/libavformat/matroskadec.c
---- a/libavformat/matroskadec.c 2018-04-20 04:02:57.000000000 -0600
-+++ b/libavformat/matroskadec.c 2018-04-24 11:02:20.779232001 -0600
-@@ -4026,6 +4026,7 @@
- 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,
-@@ -4039,6 +4040,7 @@
- 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 = {