Package: org-mode cus-test.el suggests the following variables may have incorrect custom :types. (There may be some false positives.) This refers to Org mode in current Emacs trunk.
Eg, org-texinfo-filename does not have "nil" as an option. org-agenda-deadline-leaders org-agenda-search-view-max-outline-level org-ascii-format-drawer-function org-ascii-format-inlinetask-function org-babel-latex-htlatex org-babel-latex-htlatex-packages org-babel-lob-files org-babel-python-None-to org-babel-python-mode org-babel-ruby-nil-to org-export-async-init-file org-export-with-creator org-html-format-drawer-function org-html-format-headline-function org-html-format-inlinetask-function org-html-with-latex org-latex-format-drawer-function org-latex-format-inlinetask-function org-log-note-headings org-mouse-1-follows-link org-odt-format-drawer-function org-odt-format-headline-function org-odt-format-inlinetask-function org-odt-with-latex org-plantuml-jar-path org-texinfo-filename org-texinfo-format-drawer-function org-texinfo-format-headline-function org-texinfo-format-inlinetask-function orgstruct-heading-prefix-regexp