diff --git a/libavformat/mov.c b/libavformat/mov.c
index 5a7f4a4c27..1ea8b4094a 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -5141,7 +5141,9 @@ static int mov_read_packet(AVFormatContext *s, AVPacket *pkt)
     } else {
         int64_t next_dts = (sc->current_sample < st->nb_index_entries) ?
             st->index_entries[sc->current_sample].timestamp : st->duration;
-        pkt->duration = next_dts - pkt->dts;
+
+        if (next_dts >= pkt->dts)
+            pkt->duration = next_dts - pkt->dts;
         pkt->pts = pkt->dts;
     }
     if (st->discard == AVDISCARD_ALL)