diff --git a/lisp/subr.el b/lisp/subr.el
index 3e4808c5471..58ec642dd92 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -3799,7 +3799,8 @@ like) while `y-or-n-p' is running)."
                     ;; If the minibuffer is already active, the
                     ;; selected window might not change.  Disable
                     ;; text conversion by hand.
-                    (set-text-conversion-style text-conversion-style)
+                    (when (fboundp 'set-text-conversion-style)
+                      (set-text-conversion-style text-conversion-style))
                     (read-from-minibuffer
                      prompt nil keymap nil
                      (or y-or-n-p-history-variable t)))))