diff --git a/libavformat/avidec.c b/libavformat/avidec.c
index a73bf98474..d6dea6e9bf 100644
--- a/libavformat/avidec.c
+++ b/libavformat/avidec.c
@@ -685,6 +685,7 @@ static int avi_read_header(AVFormatContext *s)
             default:
                 av_log(s, AV_LOG_INFO, "unknown stream type %X\n", tag1);
             }
+            ast->sample_size = FFMAX(ast->sample_size, 0);
             if (ast->sample_size == 0) {
                 st->duration = st->nb_frames;
                 if (st->duration > 0 && avi->io_fsize > 0 && avi->riff_end > avi->io_fsize) {