diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
index 23c6b913af0..095c89235ae 100644
--- a/lisp/progmodes/project.el
+++ b/lisp/progmodes/project.el
@@ -1608,16 +1608,15 @@ The current buffer's `default-directory' is available as part of
   (dired (project-root (project-current t))))
 
 ;;;###autoload
-(defun project-vc-dir (&optional truenameize)
+(defun project-vc-dir ()
   "Run VC-Dir in the current project's root.
 If TRUENAMEIZE is non-nil, as it is interactively, then if the project
 root is a symbolic link, resolve it first.  This matches the behaviour
 of \\[vc-dir] when invoked interactively."
-  (interactive "p")
-  (let ((root (project-root (project-current t))))
-    (vc-dir (if truenameize
-                (abbreviate-file-name (file-truename root))
-              root))))
+  (declare (interactive-only vc-dir))
+  (interactive)
+  (vc-dir (abbreviate-file-name
+           (file-truename (project-root (project-current t))))))
 
 ;;;###autoload
 (defun project-customize-dirlocals ()