diff --git a/src/code/fd-stream.lisp b/src/code/fd-stream.lisp
index 85aa0b8c3c52095b5f830ab1eccbd0f6c5dd64c6..5f194a010c12c860758d3140ae1f1b4115c034ab 100644
--- a/src/code/fd-stream.lisp
+++ b/src/code/fd-stream.lisp
@@ -1367,7 +1367,8 @@
 	   (flet ((add-suffix (list suffix)
 		    (let ((list* nil))
 		      (dolist (coding list)
-			(push (format nil "~A-~A" coding suffix) list*))
+			(push (concatenate 'simple-string coding "-" suffix)
+			      list*))
 		      (nreverse list*))))
 	     `((,target ,@list)
 	       ((,target :unix) ,@(add-suffix list "unix"))