diff --git a/libavformat/gif.c b/libavformat/gif.c
index 68320c6f23..e817121440 100644
--- a/libavformat/gif.c
+++ b/libavformat/gif.c
@@ -33,10 +33,11 @@ static int gif_image_write_header(AVFormatContext *s, int width, int height,
 {
     AVIOContext *pb = s->pb;
     AVRational sar = s->streams[0]->codec->sample_aspect_ratio;
-    int i, aspect = 0;
+    int i;
+    int64_t aspect = 0;
 
     if (sar.num > 0 && sar.den > 0) {
-        aspect = sar.num * 64 / sar.den - 15;
+        aspect = sar.num * 64LL / sar.den - 15;
         if (aspect < 0 || aspect > 255)
             aspect = 0;
     }
diff --git a/libavformat/img2enc.c b/libavformat/img2enc.c
index 684ed1441e..37dfbecce3 100644
--- a/libavformat/img2enc.c
+++ b/libavformat/img2enc.c
@@ -194,7 +194,7 @@ AVOutputFormat ff_image2_muxer = {
     .long_name      = NULL_IF_CONFIG_SMALL("image2 sequence"),
     .extensions     = "bmp,dpx,jls,jpeg,jpg,ljpg,pam,pbm,pcx,pgm,pgmyuv,png,"
                       "ppm,sgi,tga,tif,tiff,jp2,j2c,j2k,xwd,sun,ras,rs,im1,im8,im24,"
-                      "sunras,webp,xbm,xface,pix",
+                      "sunras,webp,xbm,xface,pix,y",
     .priv_data_size = sizeof(VideoMuxData),
     .video_codec    = AV_CODEC_ID_MJPEG,
     .write_header   = write_header,
diff --git a/libavformat/utils.c b/libavformat/utils.c
index 10508f6ab7..207501a296 100644
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -2451,7 +2451,7 @@ static void estimate_timings_from_pts(AVFormatContext *ic, int64_t old_offset)
             st->first_dts == AV_NOPTS_VALUE &&
             st->codec->codec_type != AVMEDIA_TYPE_UNKNOWN)
             av_log(st->codec, AV_LOG_WARNING,
-                   "start time is not set in estimate_timings_from_pts\n");
+                   "start time for stream %d is not set in estimate_timings_from_pts\n", i);
 
         if (st->parser) {
             av_parser_close(st->parser);