Tuplets and cross-staff beams

[Samuel Cederlund]

Hello all,

I have a piece of code that causes lilypond to say

Drawing systems...lilypond: ../flower/include/drul-array.hh:35: T& Drul_array<T>::at(Direction) [with T = double]: Assertion `d == 1 || d == -1' failed.

the code is as follows:

  \tuplet 3/2 4 {
    <b b'>8 { \change Staff = "upper" } cess'''8[ b] ass e ess d
    { \change Staff = "lower" }
    cess b ass e ess }

in the left hand of of the piano staff. The right hand has the same notes but one octave higher. Appreciate any help,

greetings

Samuel