Povray prism not closed warning

Question

I have a prism in povray, but I keep getting a warning: Parse Warning: Prism not closed. Ignoring it. I don't understand this, start coordinate is the same as the last one. What am I doing wrong?

It should be a curve I am subtracting from another base shape.

prism {
    bezier_spline
    -6, 6, 12,

    <-1.9, 7>,<-1.9, 12>,<-1.2, 8.3>,<-1.2, 13.4>
    <-1.2, 13.4>,<-1.2, 13.4>, <-2,13.4>, <-2,13.4>
    <-2,13.3>, <-2,13.3>, <-1.9, 7>, <-1.9, 7>

    scale 0.01
  }