diff --git a/lisp/vc-hooks.el b/lisp/vc-hooks.el
index 81a18eadd87..52b4659cec6 100644
--- a/lisp/vc-hooks.el
+++ b/lisp/vc-hooks.el
@@ -481,7 +481,9 @@ and does not employ any heuristic at all."
   "Return non-nil if FILE has not changed since the last checkout."
   (let ((checkout-time (vc-file-getprop file 'vc-checkout-time))
         (lastmod (nth 5 (file-attributes file))))
-    (if checkout-time
+    (if (and checkout-time
+             ;; Tramp and Ange-FTP return this when they don't know the time.
+             (not (equal lastmod '(0 0))))
         (equal checkout-time lastmod)
       (let ((unchanged (vc-call workfile-unchanged-p file)))
         (vc-file-setprop file 'vc-checkout-time (if unchanged lastmod 0))