How to get Java MANIFEST.MF to include Maven Version Number

I have the following in my project's pom.xml which I think should display the version of Maven being used in the resulting WAR file:

<build>
...
    <plugins>
        ...
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-war-plugin</artifactId>
            <version>2.1.1</version>
            <configuration>
                <archive>
                    <manifest>
                        <addClasspath>false</addClasspath>
                    </manifest>
                    <manifestEntries>
                        <Build-Time>${maven.build.timestamp}</Build-Time>
                        <Build-Host>${agent.name}</Build-Host>
                        <Build-User>${user.name}</Build-User>
                        <Build-Maven>Maven ${maven.version}</Build-Maven>
                        <Build-Java>${java.version}</Build-Java>
                        <Build-OS>${os.name}</Build-OS>
                        <Build-Label>${project.version}</Build-Label>
                        <Build-Path>${basedir}</Build-Path>
                    </manifestEntries>
                </archive>
            </configuration>
        </plugin>
        ...
    </plugins>
...
</build>

The MANIFEST.MF that is created looks correct see below apart from the Build-Maven line in which the ${maven.version} is not substituted with the actual version number 3.0.4 in this case.

Manifest-Version: 1.0
Archiver-Version: Plexus Archiver
Created-By: Apache Maven
Built-By: stocjon
Build-Jdk: 1.6.0_35
Build-Host: 
Build-Java: 1.6.0_35
Build-Label: 1.0.0-SNAPSHOT
Build-Maven: Maven ${maven.version}
Build-OS: Windows XP
Build-Path: C:\Development\project_name
Build-Time: 15:38:50 21-Sep