How to update quantity with decimal points

[Rahmat-OnyxTec]

Hello I am trying to update cart with the quantity in decimal points but it does not update it even not giving any response. Although it is working fine while adding item to cart.

Cart::add(array(
'id' => 456, // inique row ID
'name' => 'Sample Item',
'price' => 67.99,
'quantity' => 2.75,
'attributes' = array()
));

This above code is working fine for adding to cart but the below code for updating cart is not working.

Cart::update(456, array(
'quantity' => array(
'relative' => false,
'value' => 5.5
),
));