http://www.cliki.net/asdf has this FAQ: Q: How do I query what files need to be recompiled? A: With ASDF 3, you can (asdf:required-components system :force nil :force-not nil :keep-component 'asdf:cl-source-file :keep-operation 'asdf:compile-op) However, with ASDF 3.1.6, I find that this does not work as advertised: ;;; system1.asd (asdf:defsystem :system1 :serial t :default-component-class asdf:cl-source-file.cl :components ((:file "one") (:file "two") (:file "three"))) cl-user(8): (asdf:compile-system :system1) t cl-user(9): (asdf:required-components :system1 :force nil :force-not nil :keep-component 'asdf:cl-source-file :keep-operation 'asdf:compile-op) (#<asdf/lisp-action:cl-source-file.cl "system1" "one"> #<asdf/lisp-action:cl-source-file.cl "system1" "two"> #<asdf/lisp-action:cl-source-file.cl "system1" "three">) Is there a new way to achieve the same goal?