jbake-maven-plugin does not seem to be working with asciidoctorj-diagram

[Mobe91]

I can't get jbake-maven-plugin to work with asciidoctorj-diagram.

This is my pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.mysite</groupId>
    <artifactId>website</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

        <jbake.version>2.7.0-rc.7</jbake.version>
        <jruby-complete.version>2.5.8</jruby-complete.version>
        <asciidoctorj.version>2.5.8</asciidoctorj.version>
        <asciidoctorj-diagram.version>2.2.8</asciidoctorj-diagram.version>
    </properties>

    <build>
        <plugins>
            <plugin>
                <groupId>org.jbake</groupId>
                <artifactId>jbake-maven-plugin</artifactId>
                <version>${jbake.version}</version>
                <executions>
                    <execution>
                        <id>default-generate</id>
                        <phase>generate-resources</phase>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                    </execution>
                </executions>
                <dependencies>
                    <dependency>
                        <groupId>org.jbake</groupId>
                        <artifactId>jbake-core</artifactId>
                        <version>${jbake.version}</version>
                    </dependency>
                    <dependency>
                        <groupId>org.jruby</groupId>
                        <artifactId>jruby-complete</artifactId>
                        <version>${jruby-complete.version}</version>
                    </dependency>
                    <dependency>
                        <groupId>org.asciidoctor</groupId>
                        <artifactId>asciidoctorj</artifactId>
                        <version>${asciidoctorj.version}</version>
                    </dependency>
                    <dependency>
                        <groupId>org.asciidoctor</groupId>
                        <artifactId>asciidoctorj-diagram</artifactId>
                        <version>${asciidoctorj-diagram.version}</version>
                    </dependency>
                </dependencies>
            </plugin>
        </plugins>
    </build>
</project>

I'm not sure if I even need all these plugin dependencies. I have already tried a lot of different permutations but nothing worked and I'm out of ideas.

In my jbake.properties I have

asciidoctor.option.requires=asciidoctor-diagram
asciidoctor.attributes=icons=font,imagesdir=images,imagesoutdir=../target/src/main/jbake/assets/images

Running mvn clean jbake:inline gives me the following error:

org.jruby.exceptions.LoadError: (LoadError) no such file to load -- [asciidoctor-diagram]
    at org.jruby.RubyKernel.require (org/jruby/RubyKernel.java:1017)
    at RUBY.require (uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/core_ext/kernel_require.rb:85)
    at RUBY.<main> (<script>:1)

Hope you can help me!