ClassNotFoundException when trying to run mock using maven plugin

Hi,

 I am trying to use the maven plugin to run the mocks of SOAPUI project using Maven.

 I configured everything according to the documentation:

    <pluginRepositories>
        <pluginRepository>
            <id>eviwarePluginRepository</id>
            <url>http://www.soapui.org/repository/maven2/</url>
        </pluginRepository>
    </pluginRepositories>

    <plugin>
                <groupId>com.smartbear.soapui</groupId>
                <artifactId>soapui-maven-plugin</artifactId>
                <version>5.4.0</version>
                <executions>
                    <execution>
                        <id>StartupMock</id>
                        <configuration>
                            <projectFile>cioresearch-soapui-project.xml</projectFile>
                            <mockService>MockService 1</mockService>
                            <noBlock>true</noBlock>
                        </configuration>
                        <goals>
                            <goal>mock</goal>
                        </goals>
                        <phase>process-test-classes</phase>
                    </execution>
                </executions>
            </plugin>

However, I get this class not found exception, for SoapUIMockServiceRunner. 

Do I need to add any dependency to the plugin or set some environment variable?

Caused by: org.apache.maven.plugin.PluginExecutionException: Execution StartupMock of goal com.smartbear.soapui:soapui-maven-plugin:5.4.0:mock failed: A required class was missing while executing com.smartbear.soapui:soapui-maven-plugin:5.4.0:mock: com/eviware/soapui/tools/SoapUIMockServiceRunner

Thanks!