Screen Sharing from VNC client

I manage a small number of Macs at our company. I recently upgraded one of them to Mavericks (previously all were on Snow Leopard or earlier) and have been having issues getting Screen Sharing configured to work how I would like. I currently use UltraVNC to connect to our Snow Leopard workstations. When I connect I am prompted for a VNC specific password, after that is entered I can see the user's desktop and if necessary take control. On Mavericks it seems this process has changed. I configured Screen Sharing identical to how it is on our other workstations, but now after I enter the VNC password I am shown a OS X login screen. In theory I can select the user's account from the login screen and log in, from there I can see their screen. However, I do not have the user's password and an administrator password will not let me see their session.

Is there any way for me to configure this so that it will function similar to our other workstations? Thanks.