diff --git a/libavcodec/audiotoolboxenc.c b/libavcodec/audiotoolboxenc.c
index ad2b863bb9..908b56055f 100644
--- a/libavcodec/audiotoolboxenc.c
+++ b/libavcodec/audiotoolboxenc.c
@@ -576,6 +576,7 @@ static int ffat_encode(AVCodecContext *avctx, AVPacket *avpkt,
                                      avctx->frame_size,
                            &avpkt->pts,
                            &avpkt->duration);
+        avpkt->flags |= AV_PKT_FLAG_KEY;
     } else if (ret && ret != 1) {
         av_log(avctx, AV_LOG_ERROR, "Encode error: %i\n", ret);
         return AVERROR_EXTERNAL;