diff --git a/lisp/whitespace.el b/lisp/whitespace.el
index 15c1b83fcc1..bc23a8794eb 100644
--- a/lisp/whitespace.el
+++ b/lisp/whitespace.el
@@ -2474,7 +2474,7 @@ purposes)."
   (let ((i (length vec)))
     (when (> i 0)
       (while (and (>= (setq i (1- i)) 0)
-		  (whitespace-char-valid-p (aref vec i))))
+		  (whitespace-char-valid-p (glyph-char (aref vec i)))))
       (< i 0))))