How to export ASCII armored secret key without passphrase?

[Felix E. Klee]

There’s a known issue: <https://bugs.gnupg.org/gnupg/issue2070>

Is there any workaround? For example, could I export an ASCII armored
key with a passphrase, then decrypt the exported key?

Command that failed without passphrase (the key doesn't have one):

    $ gpg --armor --export-secret-keys >key.txt

Affected version of GnuPG is 2.1.10.

With 2.0.19 I did not run into this issue.