CSS caret not workin in in IE Edge

I have a carret in a drop down menu that works correctly in all browsers except Microsoft Edge. In Microsoft Edge is the caret split in two parts with a black line in the middle. I am attaching screenshot and css declaration.

.caret {
    display: inline-block;
    width: 0px;
    height: 0px;
    margin-left: 2px;
    vertical-align: middle;
    border-top: 4px solid\9;
    border-right: 4px solid transparent;
    border-left: 4px solid transparent;
}