diff --git a/README.org b/README.org
index 02dbeea..8ea8166 100644
--- a/README.org
+++ b/README.org
@@ -1703,7 +1703,7 @@ regexp strings.
 #+caption: Ensure =xr= installation.
 #+name: lst:ensure-xr-installation
 #+begin_src emacs-lisp -n :results silent
-(when (ensure-package-installation 'xr) t)
+(ensure-package-installation 'xr)
 #+end_src
 
 * [[info:emacs#Version Control][Version Control (info)]]
@@ -1855,8 +1855,7 @@ Listing [[lst:configure-nov]] configures [[https://depp.brause.cc/nov.el/][nov.e
 #+caption: Configure =nov=.
 #+name: lst:configure-nov
 #+begin_src emacs-lisp -n :results silent
-(when (and (ensure-package-installation 'nov)
-           (fboundp 'nov-mode))
+(when (ensure-package-installation 'nov)
   (add-to-list 'auto-mode-alist `(,(rx ".epub" eos) . nov-mode)))
 #+end_src
 
@@ -1879,8 +1878,7 @@ file.
 #+caption: Setup =pdf-tools=.
 #+name: lst:setup-pdf-tools
 #+begin_src emacs-lisp -n :results silent
-(when (and (ensure-package-installation 'pdf-tools)
-           (fboundp 'pdf-loader-install))
+(when (ensure-package-installation 'pdf-tools)
   ;; Use `pdf-loader-install' for faster startup than with `pdf-tools-install'.
   (pdf-loader-install)
 
@@ -2147,9 +2145,7 @@ list detailing and motivating each listing:
             "\\documentclass[preview]{standalone}\n")))
 
 (with-eval-after-load 'ob-lisp
-  ;; Default to `sly-eval' whenever feasible:
-  (when (and (package-installed-p 'sly)
-             (fboundp 'sly-eval))
+  (when (package-installed-p 'sly)
     (setopt org-babel-lisp-eval-fn #'sly-eval)))
 #+end_src
 
@@ -3887,9 +3883,7 @@ it for this buffer is by typing {{{kbd(C-c C-e t U)}}} to export the it to a
 #+caption: Configure =writegood-mode=.
 #+name: lst:configure-writegood-mode
 #+begin_src emacs-lisp -n :results silent
-(when (and (ensure-package-installation 'writegood-mode)
-           (fboundp 'writegood-mode))
-
+(when (ensure-package-installation 'writegood-mode)
   (add-hook 'after-init-hook
             (defun on-after-change-mode-hook-enable-writegood-mode ()
               (add-hook 'after-change-major-mode-hook
@@ -3919,15 +3913,7 @@ true in case document headlines contain links.  The code in listing
 #+name: lst:setup-which-function-mode
 #+begin_src emacs-lisp -n :results silent
 (with-eval-after-load 'which-func
-  (setopt which-func-modes
-          '(emacs-lisp-mode org-mode pdf-view-mode)))
-
-;; It looks like `python-mode' does nothing when it is an element of
-;; `which-func-modes'.
-
-;; (setopt which-func-modes t)
-
-;; (setopt which-func-display 'header) ;; AFAIU, fails on my system.
+  (setopt which-func-modes '(emacs-lisp-mode org-mode pdf-view-mode)))
 #+end_src
 
 #+caption[Define functions for ~which-func-functions~]: