diff --git a/site-lisp/timeline-tools-test.el b/site-lisp/timeline-tools-test.el
index 29ecf0f..83c7256 100644
--- a/site-lisp/timeline-tools-test.el
+++ b/site-lisp/timeline-tools-test.el
@@ -119,6 +119,8 @@ CLOCK: [2018-01-08 Mon 16:00]--[2018-01-08 Mon 16:15] =>  0:15
     (should (equal (car result)
                    'user-error))))
 
+;; XXX: timeline-tools-timeline (after changing it to work on buffers instead of files)
+
 
 ;; Conflict resolution tests
 
diff --git a/site-lisp/timeline-tools.el b/site-lisp/timeline-tools.el
index dc640c3..7b1d32f 100644
--- a/site-lisp/timeline-tools.el
+++ b/site-lisp/timeline-tools.el
@@ -287,6 +287,7 @@ or END will always be in the interval [TSTART,TEND]."
            (setq times nil))))
     task-clock-times))
 
+;; XXX: make this work on buffers instead of files
 (defun timeline-tools-timeline (tstart tend &optional files)
   "Return timeline between TSTART and TEND from FILES.