Underbrace not rendered correctly

[zihlmalb]

Asciidoctor-Code:
:encoding: UTF-8
:stem:
:mathematical-format: svg

latexmath:[C_{out} =
\underbrace{\overline{C}\cdot B \cdot A}\text{1} +
\underbrace{C \cdot \overline{B} \cdot A}\text{2} +
\underbrace{C \cdot B \cdot \overline{A}}\text{3} +
\underbrace{C \cdot B \cdot A}\text{4}]

What I get with asciidoctor-pdf:

What I expect:

Command:
asciidoctor-pdf -r asciidoctor-mathematical underbrace.adoc

Versions:
asciidoctor-mathematical-0.3.5
Asciidoctor PDF 2.3.0 using Asciidoctor 2.0.1

Files:
underbrace.zip