diff --git a/ChangeLog b/ChangeLog
index 29ea9cd2cef..4833d7667b2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2006-04-10  Tim-Philipp Müller  <tim at centricular dot net>
+
+	* gst/matroska/ebml-read.c: (gst_ebml_read_sint):
+	  Don't try to modify read-only data.
+
+	* gst/matroska/matroska-demux.c:
+	(gst_matroska_demux_parse_blockgroup_or_simpleblock):
+	  Fix comment (won't crash any longer now).
+
 2006-04-10  Michael Smith  <msmith@fluendo.com>
 
 	* ext/annodex/gstcmmlenc.c: (gst_cmml_enc_set_header_on_caps):
diff --git a/gst/matroska/ebml-read.c b/gst/matroska/ebml-read.c
index fd4a48993e5..e9dbe5045c7 100644
--- a/gst/matroska/ebml-read.c
+++ b/gst/matroska/ebml-read.c
@@ -487,7 +487,6 @@ gst_ebml_read_sint (GstEbmlRead * ebml, guint32 * id, gint64 * num)
   if (!gst_ebml_read_buffer (ebml, id, &buf))
     return FALSE;
 
-  data = GST_BUFFER_DATA (buf);
   size = GST_BUFFER_SIZE (buf);
   if (size < 1 || size > 8) {
     GST_ELEMENT_ERROR (ebml, STREAM, DEMUX, (NULL),
@@ -496,10 +495,16 @@ gst_ebml_read_sint (GstEbmlRead * ebml, guint32 * id, gint64 * num)
     gst_buffer_unref (buf);
     return FALSE;
   }
+
+  buf = gst_buffer_make_writable (buf);
+
+  data = GST_BUFFER_DATA (buf);
+
   if (data[0] & 0x80) {
     negative = 1;
     data[0] &= ~0x80;
   }
+
   *num = 0;
   while (n < size) {
     *num = (*num << 8) | data[n++];
diff --git a/gst/matroska/matroska-demux.c b/gst/matroska/matroska-demux.c
index 15431369fa6..179ea9ae9c4 100644
--- a/gst/matroska/matroska-demux.c
+++ b/gst/matroska/matroska-demux.c
@@ -2274,7 +2274,7 @@ gst_matroska_demux_parse_blockgroup_or_simpleblock (GstMatroskaDemux * demux,
       }
 
       case GST_MATROSKA_ID_REFERENCEBLOCK:{
-        /* FIXME: this segfaults
+        /* FIXME: implement support for ReferenceBlock
            gint64 num;
            if (!gst_ebml_read_sint (ebml, &id, &num)) {
            res = FALSE;