Index: /trunk/ccl/level-1/l1-streams.lisp
===================================================================
--- /trunk/ccl/level-1/l1-streams.lisp	(revision 297)
+++ /trunk/ccl/level-1/l1-streams.lisp	(revision 298)
@@ -271,5 +271,6 @@
   (not (eofp stream)))
 
-(defmethod stream-filename ((stream stream)) nil)
+(defmethod stream-filename ((stream stream))
+  (report-bad-arg stream 'file-stream))