Compilation error; in css there is a gap before ::after and ::before

I have this error when I'm nesting styles in scss. Dreamweaver puts a gap between the stylename and ::before and ::after. I don't know how to get through this. Anyone could help?
Example:
IN SCSS

.page-wrapper{
         width:80%;
         margin:0 auto;
         ::after{
              content: " ";
              display: block;
              clear: both;
         }
}

IN CSS
.page-wrapper {
        width: 80%;
        margin: 0 auto; }
.page-wrapper ::after {
       content: " ";
       display: block;
       clear: both; }

There is a gap between the r and : (marked in red). How do I fix this? I know I can put it in an ordinary css style in scss but I want to solve this properly.