=== modified file 'lisp/ChangeLog'
--- lisp/ChangeLog	2013-02-07 08:50:04 +0000
+++ lisp/ChangeLog	2013-02-07 10:11:32 +0000
@@ -1,3 +1,8 @@
+2013-02-07  Jambunathan K  <kjambunathan@gmail.com>
+
+	* icomplete.el (icomplete-forward-completions)
+	(icomplete-backward-completions): Handle corner case (bug#13602).
+
 2013-02-07  Michael Albinus  <michael.albinus@gmx.de>
 
 	* vc/vc-hooks.el (vc-find-file-hook): `buffer-file-truename' can

=== modified file 'lisp/icomplete.el'
--- lisp/icomplete.el	2013-01-04 08:20:49 +0000
+++ lisp/icomplete.el	2013-02-07 10:01:09 +0000
@@ -167,8 +167,9 @@ Second entry becomes the first and can b
   (interactive)
   (let* ((comps (completion-all-sorted-completions))
 	 (last (last comps)))
+    (when comps
     (setcdr last (cons (car comps) (cdr last)))
-    (completion--cache-all-sorted-completions (cdr comps))))
+      (completion--cache-all-sorted-completions (cdr comps)))))
 
 (defun icomplete-backward-completions ()
   "Step backward completions by one entry.
@@ -178,7 +179,7 @@ Last entry becomes the first and can be
   (let* ((comps (completion-all-sorted-completions))
 	 (last-but-one (last comps 2))
 	 (last (cdr last-but-one)))
-    (when last
+    (when (consp last)			; Atleast two elements in comps
       (setcdr last-but-one (cdr last))
       (push (car last) comps)
       (completion--cache-all-sorted-completions comps))))