diff --git a/lisp/subr.el b/lisp/subr.el
index e88815fa58c..58274987d71 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -3408,7 +3408,7 @@ read-char-choice-with-read-key
     (message "%s%s" prompt (char-to-string char))
     char))
 
-(defun sit-for (seconds &optional nodisp obsolete)
+(defun sit-for (seconds &optional nodisp)
   "Redisplay, then wait for SECONDS seconds.  Stop when input is available.
 SECONDS may be a floating-point value.
 \(On operating systems that do not support waiting for fractions of a
@@ -3417,29 +3417,11 @@ sit-for
 If optional arg NODISP is t, don't redisplay, just wait for input.
 Redisplay does not happen if input is available before it starts.
 
-Value is t if waited the full time with no input arriving, and nil otherwise.
-
-An obsolete, but still supported form is
-\(sit-for SECONDS &optional MILLISECONDS NODISP)
-where the optional arg MILLISECONDS specifies an additional wait period,
-in milliseconds; this was useful when Emacs was built without
-floating point support."
-  (declare (advertised-calling-convention (seconds &optional nodisp) "22.1")
-           (compiler-macro
-            (lambda (form)
-              (if (not (or (numberp nodisp) obsolete)) form
-                (macroexp-warn-and-return
-                 (format-message "Obsolete calling convention for `sit-for'")
-                 `(,(car form) (+ ,seconds (/ (or ,nodisp 0) 1000.0)) ,obsolete)
-                 '(obsolete sit-for))))))
+Value is t if waited the full time with no input arriving, and nil otherwise."
   ;; This used to be implemented in C until the following discussion:
   ;; https://lists.gnu.org/r/emacs-devel/2006-07/msg00401.html
   ;; Then it was moved here using an implementation based on an idle timer,
   ;; which was then replaced by the use of read-event.
-  (if (numberp nodisp)
-      (setq seconds (+ seconds (* 1e-3 nodisp))
-            nodisp obsolete)
-    (if obsolete (setq nodisp obsolete)))
   (cond
    (noninteractive
     (sleep-for seconds)