--- ispell.el.orig	2010-07-05 11:31:21.000000000 +0200
+++ ispell.el	2010-07-05 13:25:03.000000000 +0200
@@ -357,21 +357,20 @@
   :group 'ispell)
 
 (defcustom ispell-alternate-dictionary
-  (cond ((file-exists-p "/usr/dict/web2") "/usr/dict/web2")
-	((file-exists-p "/usr/share/dict/web2") "/usr/share/dict/web2")
-	((file-exists-p "/usr/dict/words") "/usr/dict/words")
-	((file-exists-p "/usr/lib/dict/words") "/usr/lib/dict/words")
-	((file-exists-p "/usr/share/dict/words") "/usr/share/dict/words")
-	((file-exists-p "/usr/share/lib/dict/words")
+  (cond ((file-readable-p "/usr/dict/web2") "/usr/dict/web2")
+	((file-readable-p "/usr/share/dict/web2") "/usr/share/dict/web2")
+	((file-readable-p "/usr/dict/words") "/usr/dict/words")
+	((file-readable-p "/usr/lib/dict/words") "/usr/lib/dict/words")
+	((file-readable-p "/usr/share/dict/words") "/usr/share/dict/words")
+	((file-readable-p "/usr/share/lib/dict/words")
 	 "/usr/share/lib/dict/words")
-	((file-exists-p "/sys/dict") "/sys/dict")
-	(t "/usr/dict/words"))
-  "*Alternate dictionary for spelling help."
+	((file-readable-p "/sys/dict") "/sys/dict"))
+  "*Alternate plain word-list dictionary for spelling help."
   :type '(choice file (const :tag "None" nil))
   :group 'ispell)
 
 (defcustom ispell-complete-word-dict ispell-alternate-dictionary
-  "*Dictionary used for word completion."
+  "*Plain word-list dictionary used for word completion."
   :type '(choice file (const :tag "None" nil))
   :group 'ispell)
 
@@ -2273,6 +2272,12 @@
   (if (null lookup-dict)
       (setq lookup-dict ispell-alternate-dictionary))
 
+  (if lookup-dict
+      (unless (file-readable-p lookup-dict)
+	(error "lookup-words error: Unreadable or missing plain word-list %s."
+	       lookup-dict))
+    (error "lookup-words error: No plain word-list found at system default locations. Customize `ispell-alternate-dictionary' to set yours."))
+
   (let* ((process-connection-type ispell-use-ptys-p)
 	 (wild-p (string-match "\\*" word))
 	 (look-p (and ispell-look-p	; Only use look for an exact match.