diff --git a/libavformat/hlsenc.c b/libavformat/hlsenc.c
index 5f9a200c6e..6b913be31c 100644
--- a/libavformat/hlsenc.c
+++ b/libavformat/hlsenc.c
@@ -2241,6 +2241,7 @@ static int hls_write_packet(AVFormatContext *s, AVPacket *pkt)
 
         new_start_pos = avio_tell(vs->avf->pb);
         if (hls->segment_type != SEGMENT_TYPE_FMP4) {
+            avio_flush(oc->pb);
             vs->size = new_start_pos - vs->start_pos;
         } else {
             vs->size = new_start_pos;