Is there a way to use an older version of Java with scala-maven-plugin

Question

I would need to compile a legacy scala project (Scala version 2.8.0). The version is incompatible with JDK8. So I would like to ideally compile the project using JDK 7. I am looking for a configuration something like the following in maven-compiler-plugin.

<maven.compiler.source>1.7</maven.compiler.source>
<maven.compiler.target>1.7</maven.compiler.target>

Is there a similar configuration in scala-maven-plugin?

I have tried using "source" as suggested in the documentation of the plugin and javacargs as well. But both those options don't work.

    <plugin>
        <groupId>net.alchim31.maven</groupId>
        <artifactId>scala-maven-plugin</artifactId>
        <version>3.4.2</version>
        <executions>
            <execution>
                <goals>
                    <goal>compile</goal>
                    <goal>testCompile</goal>
                </goals>
            </execution>
        </executions>
        <configuration>
            <recompileMode>incremental</recompileMode>
            <source>1.7</source>
            <target>1.7</target>
            <javacArgs>
                <javacArg>-source</javacArg>
                <javacArg>1.7</javacArg>
                <javacArg>-target</javacArg>
                <javacArg>1.7</javacArg>
            </javacArgs>
        </configuration>
    </plugin>

Does anyone know what I am doing wrong? I don't have the option of using JDK7