diff --git a/lisp/net/tramp.el b/lisp/net/tramp.el
index b46eeb8e374..20678ec8d1a 100644
--- a/lisp/net/tramp.el
+++ b/lisp/net/tramp.el
@@ -1960,8 +1960,11 @@ version, the function does nothing."
   "Return contents of BUFFER.
 If BUFFER is not a buffer or a buffer name, return the contents
 of `current-buffer'."
-  (with-current-buffer (or buffer (current-buffer))
-    (substring-no-properties (buffer-string))))
+  (or (let ((buf (or buffer (current-buffer))))
+        (when (bufferp buf)
+          (with-current-buffer (or buffer (current-buffer))
+	    (substring-no-properties (buffer-string)))))
+      ""))
 
 (defun tramp-debug-buffer-name (vec)
   "A name for the debug buffer for VEC."