diff --git a/libavformat/tests/movenc.c b/libavformat/tests/movenc.c
index 2fd5c67e76..23a827e97c 100644
--- a/libavformat/tests/movenc.c
+++ b/libavformat/tests/movenc.c
@@ -270,6 +270,7 @@ static void mux_frames(int n, int c)
             pkt->dts = pkt->pts = audio_dts;
             pkt->stream_index = 1;
             pkt->duration = audio_duration;
+            pkt->flags |= AV_PKT_FLAG_KEY;
             audio_dts += audio_duration;
         } else {
             if (frames == end_frames)