Spring and Thymeleaf: Template mode "HTML" has not been configured

So I've tried everything I could and it turns out that probably the cause for that was that the default thymeleaf parser is for HTML5 (this means that property spring.thymeleaf.mode in application.properties file equals HTML5).

Default application.properties values: http://docs.spring.io/spring-boot/docs/current/reference/html/common-application-properties.html

The line "spring.thymeleaf.mode=HTML" from pet clinic project somehow had no effect on that project, but in mine - it did have. Turns out I was trying to switch default parser into HTML, which I didn't have. This resulted in mentioned error. Deleting or commenting this line in application.properties solved the problem.