diff --git a/libavcodec/sunrastenc.c b/libavcodec/sunrastenc.c
index 21d6fc47a0..a9b4749758 100644
--- a/libavcodec/sunrastenc.c
+++ b/libavcodec/sunrastenc.c
@@ -199,6 +199,7 @@ static int sunrast_encode_frame(AVCodecContext *avctx,  AVPacket *avpkt,
         AV_WB32(&avpkt->data[16], s->length);
 
     *got_packet_ptr = 1;
+    avpkt->flags |= AV_PKT_FLAG_KEY;
     avpkt->size = bytestream2_tell_p(&s->p);
     return 0;
 }