--- a/lisp/bytecomp.el	Mon Aug 13 10:55:35 2007 +0200
+++ b/lisp/bytecomp.el	Mon Aug 13 10:56:21 2007 +0200
@@ -3128,9 +3128,9 @@
     ;; buffer-substring used to take exactly two args, but now takes 0-3.
     ;; convert 0-2 to two args and use special bytecode operand.
     ;; convert 3 args to a normal call.
-    (cond ((= len 1) (setq form (append form '(nil nil)))
-	   (= len 2) (setq form (append form '(nil)))))
-    (cond ((= len 3) (byte-compile-two-args form))
+    (cond ((= len 1) (byte-compile-two-args (append form '(nil nil))))
+	  ((= len 2) (byte-compile-two-args (append form '(nil))))
+	  ((= len 3) (byte-compile-two-args form))
 	  ((= len 4) (byte-compile-normal-call form))
 	  (t (byte-compile-subr-wrong-args form "0-3")))))