1 files changed, 2 insertions, 0 deletions

diff --git a/lisp/vc.el b/lisp/vc.el
index b298831cb1b..4dba0fea2ae 100644
--- a/lisp/vc.el
+++ b/lisp/vc.el
@@ -2190,6 +2190,8 @@ VC's perspective on FILE, it does not register or unregister it."
    (list
     buffer-file-name
     (intern (upcase (read-string "Switch to backend: ")))))
+  (unless (vc-call-backend backend 'registered file)
+    (error "%s is not registered in %s" file backend))
   (vc-file-clearprops file)
   (vc-file-setprop file 'vc-backend backend)
   (vc-resynch-buffer file t t))