"Cannot decrypt" "Wrong key?" regression with non-empty file_key_management_filekey

I can run following script successfully with binary from 6-Dec: https://github.com/AndriiNikitin/scripts/blob/master/test_backup_rest_encryption.sh

But newly compiled binary shows "Wrong key" error at any backup attempt:

Loading encryption plugin Encryption plugin parameter : '--file_key_management_encryption_algorithm=aes_cbc'
Encryption plugin parameter : '--file_key_management_filename=/sec/keys.enc'
/test/xtrabackup: Cannot decrypt /sec/keys.enc. Wrong key?

We should have mtr test for non-empty file_key_management_filekey