missing account with separate custom.el

[ghost]

If I place Customize variable in a separate file using (load "~/.config/emacs/custom.el") than upon startup jabber is unavailable in the menu despite having (require 'jabber) in init.el
If I open corresponding Customize group tha account list is empty although variables are set properly in custom.el
Copy-pasting account name & password from custom.el to Customize form and pressing "Apply and save" makes Jabber appear in the menu and makes it usable.
Other packages doesn't have any problems with separate custom.el
I'm using jabber 0.8.0 with emacs 26.1 on ubuntu.