maven and Java 1.6

Anybody know how I modify my pom.xml to compile my Scala code with java 1.6?  Currently my plugin section looks like so

plugin>
        <groupId>org.scala-tools</groupId>
        <artifactId>maven-scala-plugin</artifactId>
        <executions>
          <execution>
            <goals>
              <goal>compile</goal>
              <goal>testCompile</goal>
            </goals>
          </execution>
        </executions>
        <configuration>
          <scalaVersion>${scala.version}</scalaVersion>
          <args>
            <arg>-target:jvm-1.5</arg>
          </args>
        </configuration>
      </plugin>


Changing "jvm-1.5" to "jvm-1.6" gives me the following error:

[WARNING]  scalac error: unknown target 'jvm-1.6'
[WARNING]  scalac -help  gives more information
[WARNING] scalac error: bad option: '-target:jvm-1.6'


Looking at scalac -help, it seems that jvm-1.6 isn't an option.

Any help would be great.  Thanks!

-Dustin