can't generate json-summary

[globalworming]

used the latest serenity-junit-starter and added

       <dependency>
            <groupId>net.serenity-bdd</groupId>
            <artifactId>serenity-json-summary-report</artifactId>
            <version>${serenity.version}</version>
        </dependency>

to the pom.xml and configured the report

            <plugin>
                <groupId>net.serenity-bdd.maven.plugins</groupId>
                <artifactId>serenity-maven-plugin</artifactId>
                <version>${serenity.version}</version>
                <configuration>
                  <tags>${tags}</tags>
                    <reports>json-summary</reports>
                </configuration>
                <executions>
                    <execution>
                        <id>serenity-reports</id>
                        <phase>post-integration-test</phase>
                        <goals>
                            <goal>aggregate</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

serenity:reports fails with

[ERROR] Failed to execute goal net.serenity-bdd.maven.plugins:serenity-maven-plugin:2.2.8:reports (default-cli) on project serenity-junit-starter: Execution default-cli of goal net.serenity-bdd.maven.plugins:serenity-maven-plugin:2.2.8:reports failed: Failed to merge template: Template not found for name "templates/json-summary.ftl".