Chameleon theme not showing error indicator in forms


I’m using Vaadin 6.7.5 and I set Chameleon as the theme to use. It works fine but in all my forms the validation error indicators aren’t showed.
I digged all .css files and I noticed that the style “v-form-errormessage” is not present. As far as I understand, that style is necessary to properly show the error messages and indicator for a failed form validation.

Am I missing something?

Thanks in advance for any help,