Why is php storm complaining about this CSS

In the followinf, PHPStorm complains about "align-items: space-between;"

which works perfectly and does exactly what I want.  Am I missing something?

div.divbody{
    height:80%;
    margin:0;
    display:flex;
    flex-direction: column;
    justify-content: space-around;
    align-items: space-between;
    background:#999;
    padding-left:3%;
    padding-right:3%;
}


Thanks,
Dave