Warning: ssh-add failed: (return code: 1; output: Invalid lifetime)

Since 2.9.1 (first of the new versions that I've tried), when I do this:
```
keychain --debug --eval --systemd --timeout 600 --quiet key1 key2
```
I get this
```
* Warning: ssh-add failed: (return code: 1; output: Invalid lifetime)
 * Error: Unable to add keys
```
When I remove `--timeout 600`, I can add the keys without an error.