diff --git a/gst/matroska/matroska-mux.c b/gst/matroska/matroska-mux.c
index 73b7a1117f..2fd6c2cdb6 100644
--- a/gst/matroska/matroska-mux.c
+++ b/gst/matroska/matroska-mux.c
@@ -1231,6 +1231,11 @@ skip_details:
     gst_matroska_mux_set_codec_id (context, GST_MATROSKA_CODEC_ID_VIDEO_VP9);
   } else if (!strcmp (mimetype, "video/x-av1")) {
     gst_matroska_mux_set_codec_id (context, GST_MATROSKA_CODEC_ID_VIDEO_AV1);
+    gst_matroska_mux_free_codec_priv (context);
+    /* Create av1C header */
+    if (codec_buf != NULL)
+      gst_buffer_extract_dup (codec_buf, 0, gst_buffer_get_size (codec_buf),
+          &context->codec_priv, &context->codec_priv_size);
   } else if (!strcmp (mimetype, "video/mpeg")) {
     gint mpegversion;