diff --git a/ffmpeg_opt.c b/ffmpeg_opt.c
index ba2df02e47..3d50d7708b 100644
--- a/ffmpeg_opt.c
+++ b/ffmpeg_opt.c
@@ -2119,7 +2119,8 @@ static int opt_target(void *optctx, const char *opt, const char *arg)
             for (j = 0; j < nb_input_files; j++) {
                 for (i = 0; i < input_files[j]->nb_streams; i++) {
                     AVCodecContext *c = input_files[j]->ctx->streams[i]->codec;
-                    if (c->codec_type != AVMEDIA_TYPE_VIDEO)
+                    if (c->codec_type != AVMEDIA_TYPE_VIDEO ||
+                        !c->time_base.num)
                         continue;
                     fr = c->time_base.den * 1000 / c->time_base.num;
                     if (fr == 25000) {