Hello, I ask for flexbox syntax error on validater

When I try to validating "flex: 0 1 auto;" or "flex: 0 0 auto" like this 
 
header {
 display: flex;
 flex: 0 0 auto;
}
 
Result is " flex-flow value can't be 'auto' "
It seems when use flex with 3 values, flex to flex-flow conversion error
Pleaes hope it fixed