section
    position: absolute
    width: 100%
    height: 100%

    header
        position: absolute
        left: 30vw
        width: 640px

        h1
            font-size: 32px
            font-weight: 700
            letter-spacing: 4px
            &:after
                width: 24px
                height: 4px
                background-color: black
                border: none
                content: ''
                display: block

CSScomb error:

/Users/Adonai/Library/Application Support/Sublime Text 3/Packages/CSScomb/node_modules/csscomb/node_modules/csscomb-core/lib/core.js:412
            throw e;
                  ^

Please check the validity of the block starting from line #1

1*| section
2 |     position: absolute
3 |     width: 100%

Gonzales PE version: 3.0.0-10
CSScomb Core version: 2.0.2