       (redisplay))
     (with-current-buffer live-py-trace-name
       (setq-local buffer-read-only 1)
-      (unless reused-buffer (toggle-truncate-lines 1)))
+      (unless reused-buffer (setq-local truncate-lines t)))
     (live-py-update-scroll
      (line-number-at-pos (window-start)) (line-number-at-pos))))
 

          live-py-version "python")

    ;; Internal variables.
    (setq-local live-py-source-last-active-window (get-buffer-window))
    ;; Create a unique name for the trace buffer.
    (setq-local live-py-trace-name

  :group 'live-py-mode
  :lighter live-py-lighter
  :keymap (let ((map (make-sparse-keymap)))
            (define-key map (kbd "C-c M-d") #'live-py-set-driver)
            (define-key map (kbd "C-c M-w") #'live-py-set-dir)
            (define-key map (kbd "C-c M-p") #'live-py-set-path)
            (define-key map (kbd "C-c M-v") #'live-py-set-version)
            map)
  (unless (buffer-file-name)
    (user-error "Current buffer has no associated file"))
  (cond
