When loading the git version of asdf under ACL 8.0, you get the following worrying message: Warning: Nested reader conditional detected on #<FILE-SIMPLE-STREAM #P"/afs/csail.mit.edu/u/j/jpalmucci/repo-install/repo- install/../asdf/asdf.lisp" for input pos 52418>. The behavior of this feature of ACL changed between ACL 7.0 and 8.0 to be more in line with the intent of the ANS specification. You should examine the code in question to make sure it does what you intend. In ACL 8.0, (list #+allegro :allegro #-allegro #+foo :foo #-foo :default) evaluates to (:allegro) instead of (:allegro :default) as in ACL 7.0 and before. See the documentation for EXCL:*WARN-ON-NESTED-READER-CONDITIONALS* and EXCL:*SHARP-PLUS-DE-FACTO-STANDARD-COMPATIBLE* for more information. Here as a patch to fix the problem.