Index: /trunk/source/compiler/optimizers.lisp
===================================================================
--- /trunk/source/compiler/optimizers.lisp	(revision 14371)
+++ /trunk/source/compiler/optimizers.lisp	(revision 14372)
@@ -2504,3 +2504,9 @@
 
 
+(define-compiler-macro concatenate (&whole w type &rest sequences)
+  (if (and (quoted-form-p type)
+           (ignore-errors (subtypep (cadr type) 'string)))
+    `(concat-to-string ,@sequences)
+    w))
+
 (provide "OPTIMIZERS")