Index: /trunk/source/lib/macros.lisp
===================================================================
--- /trunk/source/lib/macros.lisp	(revision 14293)
+++ /trunk/source/lib/macros.lisp	(revision 14294)
@@ -2116,5 +2116,5 @@
 	      (when illegal
 		(signal-program-error "Class option~p~{ ~s~} is not one of ~s"
-				      (length illegal) illegal keyvect))))
+				      (length illegal) illegal (coerce keyvect 'list)))))
 	  `(progn
 	     (when (memq ',class-name *nx-known-declarations*)