Groovy tests runned by maven doesn't display non ASCI symbols

Question

I'm using gmaven plugin to compile sources. I have got following configuration file

<plugin>
            <groupId>org.codehaus.gmaven</groupId>
            <artifactId>gmaven-plugin</artifactId>
            <version>1.3</version>
            <configuration>
                <providerSelection>1.7</providerSelection>
                <sourceEncoding>UTF-8</sourceEncoding>
            </configuration>
            <executions>
                <execution>
                    <id>compile</id>
                    <goals>
                        <goal>generateStubs</goal>
                        <goal>compile</goal>
                        <goal>generateTestStubs</goal>
                        <goal>testCompile</goal>
                    </goals>
                </execution>
            </executions>
</plugin>

If I run mvn clean install non ASCI symbols will be displayed as ? �. How can I solve it?