diff --git a/libavcodec/h264_sei.c b/libavcodec/h264_sei.c
index eb2cf8b080..cbe7b07ce6 100644
--- a/libavcodec/h264_sei.c
+++ b/libavcodec/h264_sei.c
@@ -285,7 +285,8 @@ int ff_h264_decode_sei(H264Context *h)
             av_log(h->avctx, AV_LOG_DEBUG, "SEI %d len:%d\n", type, size);
 
         if (size > get_bits_left(&h->gb) / 8) {
-            av_log(h->avctx, AV_LOG_ERROR, "SEI truncated\n");
+            av_log(h->avctx, AV_LOG_ERROR, "SEI type %d truncated at %d\n",
+                   type, get_bits_left(&h->gb));
             return AVERROR_INVALIDDATA;
         }
         next = get_bits_count(&h->gb) + 8 * size;