diff --git a/libavformat/smoothstreamingenc.c b/libavformat/smoothstreamingenc.c
index 1104d5853f..1f2a13f675 100644
--- a/libavformat/smoothstreamingenc.c
+++ b/libavformat/smoothstreamingenc.c
@@ -559,7 +559,7 @@ static int ism_write_packet(AVFormatContext *s, AVPacket *pkt)
     SmoothStreamingContext *c = s->priv_data;
     AVStream *st = s->streams[pkt->stream_index];
     OutputStream *os = &c->streams[pkt->stream_index];
-    int64_t end_dts = (c->nb_fragments + 1) * c->min_frag_duration;
+    int64_t end_dts = (c->nb_fragments + 1LL) * c->min_frag_duration;
     int ret;
 
     if (st->first_dts == AV_NOPTS_VALUE)