Ошибка сборки Gulp

Ошибка:

Message:
    app/sass/parts/_main-block.sass
Error: Invalid CSS after "main {": expected "}", was "{"
        on line 1 of app/sass/parts/_main-block.sass
        from line 23 of app/sass/main.scss
>> main { {

   ------^

Details:
    status: 1
    file: /Users/nazar/Downloads/ziegler/zieglerundkollegen/app/sass/parts/_main-block.sass
    line: 1
    column: 7
    formatted: Error: Invalid CSS after "main {": expected "}", was "{"
        on line 1 of app/sass/parts/_main-block.sass
        from line 23 of app/sass/main.scss
>> main { {

   ------^

    messageFormatted: app/sass/parts/_main-block.sass
Error: Invalid CSS after "main {": expected "}", was "{"
        on line 1 of app/sass/parts/_main-block.sass
        from line 23 of app/sass/main.scss
>> main { {

   ------^

    messageOriginal: Invalid CSS after "main {": expected "}", was "{"
    relativePath: app/sass/parts/_main-block.sass
    domainEmitter: [object Object]
    domainThrown: false

[18:33:00] 'default' errored after 155 ms

код самого файла:

main {
    color: black;    
}

В чём может быть проблема?

Формат файла - scss, подключен правильно