Element 'block', attribute 'class': 'about-us' is not a valid value of the atomic type 'blockClassType'.

I migrated M1 data to M2 using ubertheme data migration pro. When I install a theme to my site and load the home page, I am getting the following exception:

1 exception(s): Exception #0 (Magento\Framework\Config\Dom\ValidationException): Element ‘block’, attribute ‘class’: [facet ‘pattern’] The value ‘about-us’ is not accepted by the pattern ‘[A-Z][_a-zA-Z\d] ([A-Z][_a-zA-Z\d] )*’. Line: 710

Thanks in advance!