diff --git a/asdf.lisp b/asdf.lisp
index 7b450a1980e5580cd273ec4f4c1caf289e665454..b4d0635c6f6be4afc506a856658e14fc4d3a145a 100644
--- a/asdf.lisp
+++ b/asdf.lisp
@@ -250,7 +250,7 @@
   ;; This parameter isn't actually user-visible
   ;; -- please use the exported function ASDF:ASDF-VERSION below.
   ;; the 1+ hair is to ensure that we don't do an inadvertent find and replace
-  (subseq "VERSION:1.639" (1+ (length "VERSION"))))
+  (subseq "VERSION:1.640" (1+ (length "VERSION"))))
 
 (defun asdf-version ()
   "Exported interface to the version of ASDF currently installed. A string.