diff --git a/lisp/simple.el b/lisp/simple.el
index 072723cd644..13cfa3487da 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -6828,9 +6828,12 @@ other purposes."
 
 (define-minor-mode visual-line-mode
   "Toggle visual line based editing (Visual Line mode).
-With a prefix argument ARG, enable Visual Line mode if ARG is
-positive, and disable it otherwise.  If called from Lisp, enable
-the mode if ARG is omitted or nil.
+Interactively, with a prefix argument, enable
+Visual Line mode if the prefix argument is positive,
+and disable it otherwise.  If called from Lisp, toggle
+the mode if ARG is `toggle', disable the mode if ARG is
+a non-positive integer, and enable the mode otherwise
+\(including if ARG is omitted or nil or a positive integer).
 
 When Visual Line mode is enabled, `word-wrap' is turned on in
 this buffer, and simple editing commands are redefined to act on
@@ -7262,9 +7265,12 @@ Some major modes set this.")
 
 (define-minor-mode auto-fill-mode
   "Toggle automatic line breaking (Auto Fill mode).
-With a prefix argument ARG, enable Auto Fill mode if ARG is
-positive, and disable it otherwise.  If called from Lisp, enable
-the mode if ARG is omitted or nil.
+Interactively, with a prefix argument, enable
+Auto Fill mode if the prefix argument is positive,
+and disable it otherwise.  If called from Lisp, toggle
+the mode if ARG is `toggle', disable the mode if ARG is
+a non-positive integer, and enable the mode otherwise
+\(including if ARG is omitted or nil or a positive integer).
 
 When Auto Fill mode is enabled, inserting a space at a column
 beyond `current-fill-column' automatically breaks the line at a