For example, if this is a rule: :root[foo=true] ::-moz-tree-row { min-height: 32px; } The heights of the rows do not increase immediately after document.documentElement.setAttribute("foo", "true"); Sometimes, moving the mouse over the tree causes the styles to update, but often, changing a style on the parent tree element is required; for example: tree.style.border = "1px"; tree.style.border = "";