ng-select max height dropdown panel

I'm trying to set the max height of an ng-select control and I'm using the following css

ng-dropdown-panel.custom-class {
    max-height: 200px;
}

...but it isn't having the desired effect. I have [multiple]="true" and appendto="body" on the ng-select.

How can I specify the max height correctly?

I got what I needed by doing the following

html .ng-dropdown-panel .ng-dropdown-panel-items {
    max-height: 120px;
    overflow: scroll;
}