diff --git a/ChangeLog b/ChangeLog
index b9139de9a4..b8a16f49cb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2008-08-21  Sebastian Dröge  <sebastian.droege@collabora.co.uk>
+
+	* gst/matroska/matroska-demux.c:
+	(gst_matroska_demux_parse_blockgroup_or_simpleblock):
+	If the duration of a block is unknown only use the timestamp for the
+	first lace and use GST_CLOCK_TIME_NONE as duration for the following
+	laces. Otherwise every lace has the same timestamp which leads to
+	various problems. Really fixes bug #548831.
+
 2008-08-21  Sebastian Dröge  <sebastian.droege@collabora.co.uk>
 
 	* gst/wavenc/gstwavenc.c: (gst_wavenc_chain):
diff --git a/gst/matroska/matroska-demux.c b/gst/matroska/matroska-demux.c
index 8e0193d989..44471f1b28 100644
--- a/gst/matroska/matroska-demux.c
+++ b/gst/matroska/matroska-demux.c
@@ -4214,8 +4214,10 @@ gst_matroska_demux_parse_blockgroup_or_simpleblock (GstMatroskaDemux * demux,
 
     next_lace:
       size -= lace_size[n];
-      if (lace_time != GST_CLOCK_TIME_NONE)
+      if (lace_time != GST_CLOCK_TIME_NONE && duration)
         lace_time += duration / laces;
+      else
+        lace_time = GST_CLOCK_TIME_NONE;
     }
   }