diff --git a/libavformat/cafdec.c b/libavformat/cafdec.c
index 081fc9d06c..f0f307177b 100644
--- a/libavformat/cafdec.c
+++ b/libavformat/cafdec.c
@@ -89,6 +89,7 @@ static int read_desc_chunk(AVFormatContext *s)
     caf->bytes_per_packet  = avio_rb32(pb);
     st->codecpar->block_align = caf->bytes_per_packet;
     caf->frames_per_packet = avio_rb32(pb);
+    st->codecpar->frame_size = caf->frames_per_packet != 1 ? caf->frames_per_packet : 0;
     st->codecpar->ch_layout.nb_channels = avio_rb32(pb);
     st->codecpar->bits_per_coded_sample = avio_rb32(pb);