1 files changed, 4 insertions, 2 deletions

diff --git a/lisp/international/mule-diag.el b/lisp/international/mule-diag.el
index b3f3b7eb006..f9bb0439897 100644
--- a/lisp/international/mule-diag.el
+++ b/lisp/international/mule-diag.el
@@ -255,11 +255,13 @@ detailed meanings of these arguments."
                    32
                  (or (decode-char charset (+ (* row 256) i))
                      32)))              ; gap in mapping
-      ;; Don't insert a control code.
+      ;; Don't insert control codes, non-Unicode characters.
       (if (or (< ch 32) (= ch 127))
           (setq ch (single-key-description ch))
         (if (and (>= ch 128) (< ch 160))
-            (setq ch (format "%02Xh" ch))))
+            (setq ch (format "%02Xh" ch))
+          (if (> ch #x10FFFF)
+              (setq ch 32))))
       (insert "\t" ch)
       (setq i (1+ i))))
   (insert "\n"))