Maven GAE Plugin - Unable to run gae:debug

I'm having trouble running the gae:debug goal of the Maven GAE Plugin. The error I'm receiving is below. Any ideas?

I'm running it with "mvn gae:debug".

[INFO] Packaging webapp
[INFO] Assembling webapp[test-gae] in [C:\development\test-gae\target\test-gae-0.0.1-SNAPSHOT]
[INFO] Processing war project
[INFO] Webapp assembled in[56 msecs]
[INFO] Building war: C:\development\test-gae\target\test-gae-0.0.1-SNAPSHOT.war
[INFO] [statemgmt:end-fork]
[INFO] Ending forked execution [fork id: -2101914270]
[INFO] [gae:debug]
Usage: <dev-appserver> [options] <war directory>

Options:
 --help, -h                 Show this help message and exit.
 --server=SERVER            The server to use to determine the latest
  -s SERVER                   SDK version.
 --address=ADDRESS          The address of the interface on the local machine
  -a ADDRESS                  to bind to (or 0.0.0.0 for all interfaces).
 --port=PORT                The port number to bind to on the local machine.
  -p PORT
 --sdk_root=root            Overrides where the SDK is located.
 --disable_update_check     Disable the check for newer SDK versions.

EDIT: gae:run with the jvmFlags option is also giving me the same result with the below configuration.

    <plugin>
        <groupId>net.kindleit</groupId>
        <artifactId>maven-gae-plugin</artifactId>
        <version>0.5.0</version>
        <configuration>
            <jvmFlags>
                <jvmFlag>-Xdebug</jvmFlag>
                <jvmFlag>-Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=8000</jvmFlag>
            </jvmFlags>
        </configuration>
    </plugin>

It looks like this is an open issue. I have submitted a patch for this (see Issue 38).