diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index d0d2c39ac3..06a3e90837 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -848,6 +848,14 @@ vc-revert-show-diff
   :type 'boolean
   :version "24.1")

+(defcustom vc-default-root-dir nil
+  "User-specified root directory for VC operations.
+Offered as default when the VC backend fails to identify a root
+directory."
+  :type '(choice (const :tag "None" nil)
+                 (file :must-match t :tag "File"))
+  :version "27.1")
+
 ;; Header-insertion hair

 (defcustom vc-static-header-alist
@@ -2517,7 +2525,8 @@ vc-print-root-log
 	 rootdir)
     (if backend
 	(setq rootdir (vc-call-backend backend 'root default-directory))
-      (setq rootdir (read-directory-name "Directory for VC root-log: "))
+      (setq rootdir (read-directory-name "Directory for VC root-log: "
+                                         vc-default-root-dir))
       (setq backend (vc-responsible-backend rootdir))
       (unless backend
         (error "Directory is not version controlled")))