thodg/cl-unix-cybernetics

diff --git a/prepare-build.lisp b/prepare-build.lisp
index 4f04ce5..9b63b72 100644
--- a/prepare-build.lisp
+++ b/prepare-build.lisp
@@ -157,12 +157,14 @@
 (defun system-and-dependencies (name)
   (let (dependencies)
     (labels ((dfs (name)
-               (let ((sys (asdf:find-system name)))
-                 (when (and sys (not (find sys dependencies)))
-                   (locally (declare (type asdf:system sys))
-                     (format t "~& ~A" sys) (force-output)
-                     (map 'nil #'dfs (asdf:system-depends-on sys))
-                     (push sys dependencies))))))
+               (etypecase name
+                 ((or string symbol asdf:system)
+                  (let ((sys (asdf:find-system name)))
+                    (when (and sys (not (find sys dependencies)))
+                      (locally (declare (type asdf:system sys))
+                        (format t "~& ~A" sys) (force-output)
+                        (map 'nil #'dfs (asdf:system-depends-on sys))
+                        (push sys dependencies))))))))
       (dfs name)
       (nreverse dependencies))))