diff --git a/gst/matroska/matroska-demux.c b/gst/matroska/matroska-demux.c
index 1eed1603d5..daace80e82 100644
--- a/gst/matroska/matroska-demux.c
+++ b/gst/matroska/matroska-demux.c
@@ -2903,6 +2903,11 @@ gst_matroska_demux_check_subtitle_buffer (GstElement * element,
 
   data = gst_buffer_map (*buf, &size, NULL, GST_MAP_READ);
 
+  if (!data) {
+    gst_buffer_unmap (*buf, data, -1);
+    return GST_FLOW_OK;
+  }
+
   if (!sub_stream->invalid_utf8) {
     if (g_utf8_validate (data, size, NULL)) {
       goto next;