diff --git a/include/vms/ChangeLog b/include/vms/ChangeLog
index 788d8d80c..bb2dfebe8 100644
--- a/include/vms/ChangeLog
+++ b/include/vms/ChangeLog
@@ -1,3 +1,7 @@
+2012-03-08  Tristan Gingold  <gingold@adacore.com>
+
+	* lbr.h (struct vms_lhd): Add comments.
+
 2010-05-27  Tristan Gingold  <gingold@adacore.com>
 
 	* lbr.h: Improve comments.
diff --git a/include/vms/lbr.h b/include/vms/lbr.h
index bdb436aa7..fd3c256ad 100644
--- a/include/vms/lbr.h
+++ b/include/vms/lbr.h
@@ -87,7 +87,10 @@ struct vms_lhd
   unsigned char nextvbn[4];
 
   /* Free pre-allocated index block.  */
+  /* Number of free blocks.  */
   unsigned char freidxblk[4];
+  /* VBN of a simply linked list of free blocks.  The list is terminated by a
+     nul VBN.  */
   unsigned char freeidx[4];
 
   /* Highest pre-allocated index block and in use.  */