version key is missing

[Wouter1]

When you rasa train --domain domain/ you get errors

2022-10-04 09:38:53 INFO     rasa.shared.utils.validation  - The 'version' key is missing in the training data file /home/wouter/git/virtual-coach-rasa/Rasa_Bot/domain/domain_execution_dialogs.yml. Rasa Open Source will read the file as a version '3.1' file. See https://rasa.com/docs/rasa/training-data-format.
2022-10-04 09:38:53 INFO     rasa.shared.utils.validation  - The 'version' key is missing in the training data file /home/wouter/git/virtual-coach-rasa/Rasa_Bot/domain/domain_common.yml. Rasa Open Source will read the file as a version '3.1' file. See https://rasa.com/docs/rasa/training-data-format.
2022-10-04 09:38:53 INFO     rasa.shared.utils.validation  - The 'version' key is missing in the training data file /home/wouter/git/virtual-coach-rasa/Rasa_Bot/domain/domain_rescheduling_dialog.yml. Rasa Open Source will read the file as a version '3.1' file. See https://rasa.com/docs/rasa/training-data-format.
2022-10-04 09:38:53 INFO     rasa.shared.utils.validation  - The 'version' key is missing in the training data file /home/wouter/git/virtual-coach-rasa/Rasa_Bot/domain/domain_first_aid_kit.yml. Rasa Open Source will read the file as a version '3.1' file. See https://rasa.com/docs/rasa/training-data-format.
2022-10-04 09:38:53 INFO     rasa.shared.utils.validation  - The 'version' key is missing in the training data file /home/wouter/git/virtual-coach-rasa/Rasa_Bot/domain/domain_preparation_dialogs.yml. Rasa Open Source will read the file as a version '3.1' file. See https://rasa.com/docs/rasa/training-data-format.
2022-10-04 09:38:53 INFO     rasa.shared.utils.validation  - The 'version' key is missing in the training data file /home/wouter/git/virtual-coach-rasa/Rasa_Bot/domain/domain_generic.yml. Rasa Open Source will read the file as a version '3.1' file. See https://rasa.com/docs/rasa/training-data-format.
2022-10-04 09:38:53 INFO     rasa.shared.utils.validation  - The 'version' key is missing in the training data file /home/wouter/git/virtual-coach-rasa/Rasa_Bot/domain/domain_future_self_dialog.yml. Rasa Open Source will read the file as a version '3.1' file. See https://rasa.com/docs/rasa/training-data-format.
2022-10-04 09:38:53 INFO     rasa.shared.utils.validation  - The 'version' key is missing in the training data file /home/wouter/git/virtual-coach-rasa/Rasa_Bot/domain/domain_general_activity.yml. Rasa Open Source will read the file as a version '3.1' file. See https://rasa.com/docs/rasa/training-data-format.
2022-10-04 09:38:53 INFO     rasa.shared.utils.validation  - The 'version' key is missing in the training data file /home/wouter/git/virtual-coach-rasa/Rasa_Bot/domain/domain_minimum_functional_product.yml. Rasa Open Source will read the file as a version '3.1' file. See https://rasa.com/docs/rasa/training-data-format.

Fix might be as simple as adding version: "3.1" to the files, but when I tried that I got unexpected new errors.