diff --git a/libavformat/thp.c b/libavformat/thp.c
index 4463484..f2fcd5a 100644
--- a/libavformat/thp.c
+++ b/libavformat/thp.c
@@ -110,6 +110,7 @@ static int thp_read_header(AVFormatContext *s)
             st->codec->width = avio_rb32(pb);
             st->codec->height = avio_rb32(pb);
             st->codec->sample_rate = av_q2d(thp->fps);
+            st->duration = thp->framecnt;
             thp->vst = st;
             thp->video_stream_index = st->index;