How to import (RSA) secret keys?

[Matthias Bauer]

Hi,
just tried to import my old 2.x secret key with

gpg --secret-keyring .pgp/secring.pgp \
    --export-secret-key 0xTheKeyID | gpg --import

but gpg complains about ''packet(5) with unknown version 64``.
Testing with 

gpg --secret-keyring .pgp/secring.pgp \
    --export-secret-key 0xTheKeyID | gpg --list-packets

gives no error and says that the version was 3.
Obviously I missed something, but what?

Matthias