Cancelled mailing still sent

I create a mailing with a given name (e.g. "Mailing X") and submitted it for immediate sending to a group. Afterwards I noticed an error in the mailing and cancelled it successfully. I then re-used that same mailing, however instead of calling it "Copy of Mailing X" I used the original name "Mailing X". I then completed the mailing and scheduled it to be sent immediately. However, I found that the first version of Mailing X was no longer cancelled and had already completed. Is there an issue with having multiple mailings with the same name? A cancelled mailing should stay cancelled.