How to prevent ly:stencil-rotate to modify dimensions

[Thomas Morley]

Hi all,

let's say I've a stencil, which I want to rotate around it's center.
For the example below I choosed make-circle-stencil, because a circle
center-rotated _should_ always look equal.
Though, applying ly:stencil-rotate modifies the dimensions of said
circle for degrees not equal to (* 90 n).
(Made visible by boxing it)

Why?
How to prevent?

\markup
  \override #'(box-padding . 0)
  \box {
    \stencil
    #(make-circle-stencil 0.5 0.1 #f)
    \stencil
    #(ly:stencil-rotate (make-circle-stencil 0.5 0.1 #f) 10 0 0)
  }


Cheers,
  Harm