Falha ao definir o tamanho permsize ou maxpermsize com o maven-compiler-plugin (v3.2).

Eu tentei assim:

<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>      
<configuration>
    <meminitial>1024m</meminitial>
    <maxmem>2024m</maxmem>  
    <compilerArgument>-XX:PermSize=128m</compilerArgument>  
</configuration>
</plugin>

O que resulta em um erro

Caused by: org.codehaus.plexus.compiler.CompilerException: invalid flag: -XX:MaxPermSize=256m -XX:PermSize=128m
    at org.codehaus.plexus.compiler.javac.JavaxToolsCompiler.compileInProcess(JavaxToolsCompiler.java:191)
    at org.codehaus.plexus.compiler.javac.JavacCompiler.performCompile(JavacCompiler.java:169)
    at org.apache.maven.plugin.compiler.AbstractCompilerMojo.execute(AbstractCompilerMojo.java:785)
    ... 22 more
Caused by: java.lang.IllegalArgumentException: invalid flag: -XX:MaxPermSize=256m -XX:PermSize=128m
    at com.sun.tools.javac.api.JavacTool.processOptions(JavacTool.java:231)
    at com.sun.tools.javac.api.JavacTool.getTask(JavacTool.java:199)
    at com.sun.tools.javac.api.JavacTool.getTask(JavacTool.java:68)
    at org.codehaus.plexus.compiler.javac.JavaxToolsCompiler.compileInProcess(JavaxToolsCompiler.java:115)
    ... 24 more

Minha outra tentativa foi adicioná-lo como no exemplohttp://maven.apache.org/plugins/maven-compiler-plugin/examples/pass-compiler-arguments.html

<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>      
<configuration>
    <meminitial>1024m</meminitial>
    <maxmem>2024m</maxmem>  
    <compilerArguments>
        <Xms>128m</Xms>
        <Xmx>1024m</Xmx>                        
        <XX:MaxPermSize>256m</XX:MaxPermSize>
        <XX:PermSize>128m</XX:PermSize>                                              
    </compilerArguments>
</configuration>
</plugin>

Resultando no mesmo erro:

Caused by: org.codehaus.plexus.compiler.CompilerException: invalid flag: -XX:MaxPermSize
    at org.codehaus.plexus.compiler.javac.JavaxToolsCompiler.compileInProcess(JavaxToolsCompiler.java:191)
    at org.codehaus.plexus.compiler.javac.JavacCompiler.performCompile(JavacCompiler.java:169)
    at org.apache.maven.plugin.compiler.AbstractCompilerMojo.execute(AbstractCompilerMojo.java:785)
    ... 22 more
Caused by: java.lang.IllegalArgumentException: invalid flag: -XX:MaxPermSize
    at com.sun.tools.javac.api.JavacTool.processOptions(JavacTool.java:231)
    at com.sun.tools.javac.api.JavacTool.getTask(JavacTool.java:199)
    at com.sun.tools.javac.api.JavacTool.getTask(JavacTool.java:68)
    at org.codehaus.plexus.compiler.javac.JavaxToolsCompiler.compileInProcess(JavaxToolsCompiler.java:115)
    ... 24 more

então, por que esse sinalizador é inválido? Se isso for levado em consideração quando eu adiciono à variável MVN_OPTS?