tar command error message "5694 Aborted"

When using the GNU tar utility on Redhat today I was getting:
5694 Aborted                 tar --verbose --append --gzip --file myfile.tarz .......

I believe this is caused by trying to append to a compressed tar file.

It's OK on the first command, with the --gzip (-z) and --create (-c)

But when I try to add to that file with --gzip and --append, I get the error.

If I remove the --gzip from both commands (and take the "z" out of the file extension), it seems to work as expected.

I imagine I could compress the resulting tar file after all the appends are done.