Change height not possible in css

[yormy]

When I override the css style for the height of the boxes

.ms-container .ms-list{
    heigth:500px !important;
    padding-left:99px;
}

It still uses the height defined in the original multi-select.css (which is ofcourse loaded before my overrides)
When I remove the height from the original it reacts like a dynamically resizing selectbox
Any ideas on how I can change the height in the override ?