diff --git a/libavcodec/h264.c b/libavcodec/h264.c
index f45c572a41..658d865339 100644
--- a/libavcodec/h264.c
+++ b/libavcodec/h264.c
@@ -3867,8 +3867,14 @@ again:
 
                 if (s->flags & CODEC_FLAG_LOW_DELAY ||
                     (h->sps.bitstream_restriction_flag &&
-                     !h->sps.num_reorder_frames))
-                    s->low_delay = 1;
+                     !h->sps.num_reorder_frames)) {
+                    if (s->avctx->has_b_frames > 1 || h->delayed_pic[0])
+                        av_log(avctx, AV_LOG_WARNING, "Delayed frames seen "
+                               "reenabling low delay requires a codec "
+                               "flush.\n");
+                        else
+                            s->low_delay = 1;
+                }
 
                 if (avctx->has_b_frames < 2)
                     avctx->has_b_frames = !s->low_delay;