diff --git a/lisp/net/tramp.el b/lisp/net/tramp.el
index c6665c27924..9d5a02456ec 100644
--- a/lisp/net/tramp.el
+++ b/lisp/net/tramp.el
@@ -1955,7 +1955,8 @@ The outline level is equal to the verbosity of the Tramp message."
   "A predicate for Tramp interactive commands.
 They are completed by \"M-x TAB\" only in Tramp debug buffers."
   (with-current-buffer buffer
-    (string-equal (buffer-substring 1 (min 10 (point-max))) ";; Emacs:")))
+    (string-equal
+     (buffer-substring (point-min) (min 10 (point-max))) ";; Emacs:")))
 
 (put #'tramp-debug-buffer-command-completion-p 'tramp-suppress-trace t)