The includes/excludes feature on the dependency:unpack goal does not work for artifacts of type tar.gz

I am trying to unpack an artifact of type tar.gz and filter some of the files. Nothing is filtered. This works for artifacts of type zip, but not tar.gz.

<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<version>2.1</version>
<executions>
<execution>
<id>modules</id>
<phase>process-resources</phase>
<goals>
<goal>unpack</goal>
</goals>
<configuration>
<artifactItems>
<!-- Doesn't Work -->
<artifactItem>
<groupId>org.apache.maven</groupId>
<artifactId>apache-maven</artifactId>
<type>tar.gz</type>
<classifier>src</classifier>
<version>2.2.1</version>
<outputDirectory>out1</outputDirectory>
<excludes>*/.txt</excludes>
</artifactItem>
<!-- Works -->
<artifactItem>
<groupId>org.apache.maven</groupId>
<artifactId>apache-maven</artifactId>
<type>zip</type>
<classifier>src</classifier>
<version>2.2.1</version>
<outputDirectory>out2</outputDirectory>
<excludes>*/.txt</excludes>
</artifactItem>
</artifactItems>
</configuration>
</execution>
</executions>
</plugin>

log output:
C:\tmp>mvn process-resources
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Building FabricServer Installer
[INFO] task-segment: [process-resources]
[INFO] ------------------------------------------------------------------------
[INFO] [resources:resources

]
[WARNING] Using platform encoding (Cp1252 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory C:\tmp\src\main\resources
[INFO] [dependency:unpack

]
[INFO] Configured Artifact: org.apache.maven:apache-maven:src:2.2.1:tar.gz
[INFO] Configured Artifact: org.apache.maven:apache-maven:src:2.2.1:zip
[INFO] Unpacking C:\Documents and Settings\xxxx\.m2\repository\org\apache\maven\apache-maven\2.2.1\apache-maven-2.2.1-
src.tar.gz to
C:\tmp\out1
with includes null and excludes:*/.txt
[INFO] Expanding C:\Documents and Settings\xxxx\.m2\repository\org\apache\maven\apache-maven\2.2.1\apache-maven-2.2.1-
src.tar.gz to C:\DOCUME~1\bengel\LOCALS~1\Temp\tmp1546101557682884989.tar
[INFO] Expanding: C:\DOCUME~1\bengel\LOCALS~1\Temp\tmp1546101557682884989.tar into C:\tmp\out1
[INFO] Unpacking C:\Documents and Settings\xxxx\.m2\repository\org\apache\maven\apache-maven\2.2.1\apache-maven-2.2.1-
src.zip to
C:\tmp\out2
with includes null and excludes:*/.txt
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 17 seconds
[INFO] Finished at: Thu Sep 30 15:20:28 EDT 2010
[INFO] Final Memory: 13M/24M
[INFO] ------------------------------------------------------------------------