dropdownStyles={{ zIndex: 999 }}   no working

<SelectList
            setSelected={setDid}
            data={DYNASTYS.map((dynasty, index) => ({
              key: index.toString(),
              value: dynasty
            }))}
            save="key"
            dropdownStyles={{ zIndex: 999 }}
            defaultOption={{
              key: did,
              value: DYNASTYS[did]
            }}