diff --git a/doc/source/index.rst b/doc/source/index.rst
index 28ca1ff..ea9e537 100644
--- a/doc/source/index.rst
+++ b/doc/source/index.rst
@@ -318,7 +318,6 @@ Notebook
 ^^^^^^^^
 
 .. el:variable:: ein:worksheet-enable-undo
-.. el:variable:: ein:notebook-discard-output-on-save
 .. el:variable:: ein:notebook-modes
 .. el:variable:: ein:notebook-kill-buffer-ask
 .. el:variable:: ein:notebook-querty-timeout-open
@@ -498,6 +497,7 @@ Change Log
 v0.2
 ----
 
+* :el:symbol:`ein:notebook-discard-output-on-save` is obsolete now.
 * Support execution history.  Commands
   :el:symbol:`ein:worksheet-previous-input-history` and
   :el:symbol:`ein:worksheet-next-input-history` can be used
diff --git a/lisp/ein-notebook.el b/lisp/ein-notebook.el
index 4d41ee2..44e9364 100644
--- a/lisp/ein-notebook.el
+++ b/lisp/ein-notebook.el
@@ -56,9 +56,15 @@
 
 ;;; Configuration
 
+(make-obsolete-variable 'ein:notebook-discard-output-on-save nil "0.2.0")
+
 (defcustom ein:notebook-discard-output-on-save 'no
   "Configure if the output part of the cell should be saved or not.
 
+.. warning:: This configuration is obsolete now.
+   Use nbconvert (https://github.com/ipython/nbconvert) to
+   strip output.
+
 `no' : symbol
     Save output. This is the default.
 `yes' : symbol
@@ -68,16 +74,9 @@ a function
     `t' to discard output and return `nil' to save.  For example,
     if you don't want to save image output but other kind of
     output, use `ein:notebook-cell-has-image-output-p'.
-
-Note that using function needs EIN lisp API, which is not determined
-yet.  So be careful when using EIN functions.  They may change."
-  ;; FIXME: Change call signature of the function.  Like this:
-  ;;          (funcall FUNC :cell cell :worksheet ws :notebook notebook)
+"
   :type '(choice (const :tag "No" 'no)
                  (const :tag "Yes" 'yes)
-                 ;; FIXME: this must be go to the customize UI after
-                 ;; clarifying the notebook lisp API.
-                 ;; (function :tag "Predicate" (lambda () t))
                  )
   :group 'ein)
 
diff --git a/lisp/ein-worksheet.el b/lisp/ein-worksheet.el
index 3ad901e..7a6db30 100644
--- a/lisp/ein-worksheet.el
+++ b/lisp/ein-worksheet.el
@@ -80,6 +80,9 @@ this value."
 (defclass ein:worksheet ()
   ((nbformat :initarg :nbformat :type integer)
    (get-notebook-name :initarg :get-notebook-name :type cons)
+   ;; This slot introduces too much complexity so therefore must be
+   ;; removed later.  This is here only for backward compatible
+   ;; reason.
    (discard-output-p :initarg :discard-output-p)
    (data :initarg :data)
    (ewoc :initarg :ewoc :type ewoc)