Remapping the universal argument does not work with elpy

[joemrt]

In my emacs config I remap C-u to C-S-u (that is Control-Shift-U) via

(global-set-key (kbd "C-S-u") 'universal-argument)
(define-key universal-argument-map (kbd "C-S-u") 'universal-argument)

While this is working fine with other packages, elpy seems not to recognize this new prefix key and just behaves as if there is was no prefix key pressed. I also tried to exchange universal-argument by universal-argument-more.

Is C-u somehow hardwired into the package or is there maybe some elpa keymap where I have to include my mapping? (I also tried to include the binding in elpy-mode-map and elpy-shell-map but this led to nothing)