How to prevent slur from breaking?

Hi.

When it comes to create slur over repeat (volta), I use this trick:

http://lilypond.org/doc/v2.19/Documentation/notation/modifying-shapes#modifying-ties-and-slurs (see: Specifying control points explicitly)

But when slur is created just before line break, it appears also in the next line, which of course is not what I want.

c'1 c'1 c'1 c'1 c'1 c'1 c'1 c'1 c'1 c'1 c'1 c'1 -\tweak control-points #'((-46 . 7) (-31 . 8) (-9 . 9) (0.75 . 7)) ( <> ) c'1 c'1 c'1 c'1 c'1 c'1 c'1 c'1 c'1 c'1 c'1 c'1 c'1 c'1

How to prevent this?

--Karol