You can catch this with yamllint (https://github.com/adrienverge/yamllint https://github.com/adrienverge/yamllint): % cat countries.yml --- countr

You can catch this with yamllint (https://github.com/adrienverge/yamllint https://github.com/adrienverge/yamllint): % cat countries.yml --- countries: - US - GB - NO - FR % yamllint countries.yml countries.yml 5:4 warning truthy value should be one of [false, true] (truthy)