+(defcustom lisp-indent-backquote-substitution-mode t
+ "How to indent substitutions in backquotes.
+If t, the default, indent substituted forms normally.
+If nil, do not apply special indentation rule to substituted
+forms. If `corrected', subtract the `,' or `,@' from the form
+column, indenting as if this character sequence were not present.
+In any case, do not backtrack beyond a backquote substitution.
+
+Until Emacs 25.1, the nil behavior was hard-wired."
+ :version "25.1"
+ :type '(choice (const corrected) (const nil) (const t))
+ :group 'lisp-indent)
+