diff --git a/gst/matroska/matroska-mux.c b/gst/matroska/matroska-mux.c
index 265eb186db..e3d9ab1a01 100644
--- a/gst/matroska/matroska-mux.c
+++ b/gst/matroska/matroska-mux.c
@@ -2681,13 +2681,15 @@ gst_matroska_mux_write_data (GstMatroskaMux * mux, GstMatroskaPad * collect_pad)
 
     return gst_ebml_last_write_result (ebml);
   } else {
+    int flags =
+        GST_BUFFER_FLAG_IS_SET (buf, GST_BUFFER_FLAG_DELTA_UNIT) ? 0 : 0x80;
     gst_ebml_write_set_cache (ebml, GST_BUFFER_SIZE (buf) * 2);
     /* write and call order slightly unnatural,
      * but avoids seek and minizes pushing */
     blockgroup = gst_ebml_write_master_start (ebml, GST_MATROSKA_ID_BLOCKGROUP);
     hdr =
         gst_matroska_mux_create_buffer_header (collect_pad->track,
-        relative_timestamp, 0);
+        relative_timestamp, flags);
     if (write_duration) {
       gst_ebml_write_uint (ebml, GST_MATROSKA_ID_BLOCKDURATION,
           gst_util_uint64_scale (block_duration, 1, mux->time_scale));