diff --git a/libavcodec/libx264.c b/libavcodec/libx264.c
index b680e2098e..e8ca3d896b 100644
--- a/libavcodec/libx264.c
+++ b/libavcodec/libx264.c
@@ -596,6 +596,8 @@ static int X264_frame(AVCodecContext *ctx, AVPacket *pkt, const AVFrame *frame,
         wallclock = out_opaque->wallclock;
     } else {
         // Unexpected opaque pointer on picture output
+        av_log(ctx, AV_LOG_ERROR, "Unexpected opaque pointer; "
+               "this is a bug, please report it.\n");
         ctx->reordered_opaque = 0;
     }