ListView's TopItem property not working as expected

I'm setting the TopItem property of a ListView item like so:

listViewObj.TopItem = listViewObj.Items[newTopIndex]; //newTopIndex = 192
newTopIndex = listViewObj.TopItem.Index; //newTopIndex = 190?

In debugging, newTopIndex was 192 when setting TopItem. After setting listViewObj.TopItem, newTopIndex was assigned 190. These calls are literally one after the other; nothing else happens between. Is there something wrong with this syntax?