diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog
index a9f6c01b73e..226e03fc5b8 100644
--- a/doc/lispref/ChangeLog
+++ b/doc/lispref/ChangeLog
@@ -1,3 +1,8 @@
+2009-07-15  Chong Yidong  <cyd@stupidchicken.com>
+
+	* markers.texi (The Mark): Document optional arg to
+	deactivate-mark.
+
 2009-07-11  Kevin Ryde  <user42@zip.com.au>
 
 	* hooks.texi (Standard Hooks): Fix cross-references.
diff --git a/doc/lispref/markers.texi b/doc/lispref/markers.texi
index 78dbbefd790..d4321362cc9 100644
--- a/doc/lispref/markers.texi
+++ b/doc/lispref/markers.texi
@@ -576,9 +576,10 @@ modification.  For example:
 @end example
 @end defvar
 
-@defun deactivate-mark
-This function deactivates the mark, if Transient Mark mode is enabled.
-Otherwise it does nothing.
+@defun deactivate-mark &optional force
+This function deactivates the mark, provided Transient Mark mode is
+enabled or @var{force} is non-@code{nil}.  Deactivating the mark also
+runs @code{deactivate-mark-hook}, described below.
 @end defun
 
 @defvar mark-active