diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
index 188236427da..08798d86f8e 100644
--- a/lisp/progmodes/project.el
+++ b/lisp/progmodes/project.el
@@ -396,8 +396,6 @@ backend implementation of `project-external-roots'.")
        (setq files
              (mapcar
               (lambda (file) (concat default-directory file))
-              ;; XXX: With large enough project, split-string becomes
-              ;; one of the bottlenecks.
               (split-string
                (apply #'vc-git--run-command-string nil "ls-files" args)
                "\0" t)))