scheme tweak doesn't work anymore

[Stefan Thomas]

Dear community,
because I have unhappy with the placement of the tenuto-sign in combination with the accent, I've made a little scheme-script for to change it.
Unfortunately, it doesn't work any more, and I don't know, what could be the reason.
Here is ve short example:
\version "2.13.0"
ta = #(define-music-function (parser location x) (ly:music?)
     #{
        \context Voice <<     $x  { s1 *0 -\tweak \once \override Script #'extra-offset = #'(6.2 . -5.6) -- -> } >>
     #})

{ \ta  c''1  }