diff --git a/libavformat/swfenc.c b/libavformat/swfenc.c
index 84f924eda5..9da4aad959 100644
--- a/libavformat/swfenc.c
+++ b/libavformat/swfenc.c
@@ -256,7 +256,7 @@ static int swf_write_header(AVFormatContext *s)
         av_log(s, AV_LOG_ERROR, "Invalid (too large) frame rate %d/%d\n", rate, rate_base);
         return AVERROR(EINVAL);
     }
-    avio_wl16(pb, (rate * 256) / rate_base); /* frame rate */
+    avio_wl16(pb, (rate * 256LL) / rate_base); /* frame rate */
     swf->duration_pos = avio_tell(pb);
     avio_wl16(pb, (uint16_t)(DUMMY_DURATION * (int64_t)rate / rate_base)); /* frame count */