diff --git a/lisp/mouse.el b/lisp/mouse.el
index 07e593a70c1..03740e780d5 100644
--- a/lisp/mouse.el
+++ b/lisp/mouse.el
@@ -1857,7 +1857,7 @@ and selects that window."
 			    (string< (buffer-name elt1) (buffer-name elt2))))))
     (setq tail buffers)
     (while tail
-      (or (eq ?\ (aref (buffer-name (car tail)) 0))
+      (or (eq ?\s (aref (buffer-name (car tail)) 0))
 	  (setq maxlen
 		(max maxlen
 		     (length (buffer-name (car tail))))))