diff --git a/libavformat/aqtitledec.c b/libavformat/aqtitledec.c
index 81630d73b0..960a5d8ef5 100644
--- a/libavformat/aqtitledec.c
+++ b/libavformat/aqtitledec.c
@@ -74,7 +74,8 @@ static int aqt_read_header(AVFormatContext *s)
             new_event = 1;
             pos = avio_tell(s->pb);
             if (sub) {
-                sub->duration = frame - sub->pts;
+                if (frame >= sub->pts && (uint64_t)frame - sub->pts < INT64_MAX)
+                    sub->duration = frame - sub->pts;
                 sub = NULL;
             }
         } else if (*line) {