[Solved] Voucher - for category not total

[kiwi1066]

Hi

I am looking at using vouchers, this is what is happening.
I have setup a value voucher of $30 for category X products,
I select a product from category Y , value $15, and add the voucher in the checkout process, Error message appears saying that the voucher is not for that product. This is as expected.
Then I add a second product from category X, value $10, I add the voucher code and click Add.
The voucher is added to the cart and the Cart Total is $0
The voucher has been applied to both products when it should only be applied to the category X product leaving a Total of $15 to pay.

Can someone tell what I may be doing wrong or id this a bug?

PS v1.4.1

Update:
Has been listed as bug, and entered as future enhancement