behavior.el includes this: ;; List of enabled behaviors. (defcustom enabled-behavior-list nil "List of currently enabled behaviors. Normally, don't set it directly; use `enable-behavior' or `disable-behavior'." :initialize #'set-default :set #'(lambda (sym val) (if within-behavior-enabling-disabling (set sym val) (let* ((old-val enabled-behavior-list) (disable-list (set-difference old-val val)) (enable-list (set-difference val old-val))) (dolist (b disable-list) (disable-behavior b t)) (dolist (b enable-list) (enable-behavior b t)) (assert (equal enabled-behavior-list val))))) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ :type '(repeat (symbol :tag "Behavior")) :group 'behaviors) At startup, custom-set-variables calls it with (resize-minibuffer recent-files mwheel jka-compr func-menu filladapt efs) as a parameter. The set method does its work, end ends up with (efs filladapt func-menu jka-compr mwheel recent-files resize-minibuffer) as a result. Hence, the assert fails. So the problem is obvious (the list is commutative, equal isn't), but I don't know how to fix it (short of dropping the assert entirely). Do we have an equal-commutative or something? OG.