diff --git a/gnu/packages/lisp.scm b/gnu/packages/lisp.scm
index a5df90869a..c98f6015c1 100644
--- a/gnu/packages/lisp.scm
+++ b/gnu/packages/lisp.scm
@@ -5234,6 +5234,7 @@ (define-public sbcl-lack
        (uri (git-reference
              (url "https://github.com/fukamachi/lack.git")
              (commit commit)))
+       (file-name (git-file-name "lack" version))
        (sha256
         (base32 "1avh4ygcj9xcx4m17nj0wnxxaisk26w4ljs2bibzxaln24x7pi85"))))
      (build-system asdf-build-system/sbcl)