diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index e352ed8..73c9212 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -4242,7 +4242,9 @@
 'imactivatefunc' 'imaf'	string (default "")
 			global
 	This option specifies a function that will be called to
-	activate or deactivate the Input Method.
+	activate or deactivate the Input Method.  The value can be the name of
+	a function, a |lambda| or a |Funcref|. See |option-value-function| for
+	more information.
 	It is not used in the MS-Windows GUI version.
 	The expression will be evaluated in the |sandbox| when set from a
 	modeline, see |sandbox-option|.
@@ -4352,6 +4354,8 @@
 			global
 	This option specifies a function that is called to obtain the status
 	of Input Method.  It must return a positive number when IME is active.
+	The value can be the name of a function, a |lambda| or a |Funcref|.
+	See |option-value-function| for more information.
 	It is not used in the MS-Windows GUI version.
 
 	Example: >