diff --git a/mps/design/range.txt b/mps/design/range.txt
index ee1e734ea40..f65bb10e744 100644
--- a/mps/design/range.txt
+++ b/mps/design/range.txt
@@ -40,9 +40,10 @@ Interface
 
 ``typedef RangeStruct *Range``
 
-``Range`` is the type of a range. It is an alias for ``RangeStruct *``. ``RangeStruct`` is defined in the header so that it can be
-inlined in client structures or allocated on the stack. Clients must
-not depend on its implementation details.
+``Range`` is the type of a range. It is an alias for
+``RangeStruct *``. ``RangeStruct`` is defined in the header so that it
+can be inlined in client structures or allocated on the stack. Clients
+must not depend on its implementation details.
 
 ``void RangeInit(Range range, Addr base, Addr limit)``
 
@@ -78,6 +79,18 @@ there is a function too.)
 Return the limit of the range. (This is implemented as a macro, but
 there is a function too.)
 
+``void RangeSetBase(Range range, Addr addr)``
+
+Set the base of the range.  ``addr`` must not be greater than the
+range limit.  To set them both at once, use ``RangeInit``.  (This is
+implemented as a macro, but there is a function too.)
+
+``void RangeSetLimit(Range range, Addr addr)``
+
+Set the limit of the range.  ``addr`` must not be less than the range
+base.  To set the both at once, use ``RangeInit``.  (This is
+implemented as a macro, but there's a function too.)
+
 ``Size RangeSize(Range range)``
 
 Return the size of the range. (This is implemented as a macro, but
@@ -117,14 +130,16 @@ Document history
 
 - 2013-05-21 GDR_ Created.
 - 2014-01-15 GDR_ Added ``RangeContains``.
+- 2016-03-27 RB_ Addded ``RangeSetBase`` and ``RangeSetLimit``.
 
 .. _GDR: http://www.ravenbrook.com/consultants/gdr/
+.. _RB: http://www.ravenbrook.com/consultants/rb/
 
 
 Copyright and License
 ---------------------
 
-Copyright © 2013-2014 Ravenbrook Limited <http://www.ravenbrook.com/>.
+Copyright © 2013-2016 Ravenbrook Limited <http://www.ravenbrook.com/>.
 All rights reserved. This is an open source license. Contact
 Ravenbrook for commercial licensing options.