diff --git a/lisp/subr.el b/lisp/subr.el
index ce49604f811..00a947397ae 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -2312,7 +2312,8 @@ floating point support."
 (declare-function x-popup-dialog "menu.c" (position contents &optional header))
 
 (defun y-or-n-p (prompt)
-  "Ask user a \"y or n\" question.  Return t if answer is \"y\".
+  "Ask user a \"y or n\" question.
+Return t if answer is \"y\" and nil if it is \"n\".
 PROMPT is the string to display to ask the question.  It should
 end in a space; `y-or-n-p' adds \"(y or n) \" to it.