diff --git a/lisp/emacs-lisp/loaddefs-gen.el b/lisp/emacs-lisp/loaddefs-gen.el
index d4c0a87e6f9..6a40b3d84b0 100644
--- a/lisp/emacs-lisp/loaddefs-gen.el
+++ b/lisp/emacs-lisp/loaddefs-gen.el
@@ -662,7 +662,14 @@ instead of just updating them with the new/changed autoloads."
                                 (file-attributes file))))
           ;; If we're scanning for package versions, we want to look
           ;; at the file even if it's excluded.
-          (let* ((excluded (member file excluded-files))
+          (let* ((excluded
+                  ;; FIXME: In out-of-tree builds (bug#79694) `excluded.files'
+                  ;; (derived via `lisp-directory' from `invocation-directory')
+                  ;; may end up using names which don't quite match those of
+                  ;; `file' (derived from the command line arguments), w.r.t
+                  ;; "c:" vs "C:", so use a test more lax than `member'.
+                  (let ((x (member-ignore-case file excluded-files)))
+                    (and x (file-equal-p file (car x)))))
                  (package-data
                   (and include-package-version (if excluded 'only t))))
             (when (or package-data (not excluded))