Updating avast causes not enough space error

I have two hard drives in my machine. An SSD for the OS and programs I used often, and a second harddrive for all my data and other programs. I’m running WIndows 7 x64.

I’ve installed avast on the secondary hard drive which has over 1TB free space currently. When Avast tries to update I get an error that there is not enough space on the disk. I assume this means it’s trying to download files to the OS drive which is smaller and probably doesn’t have the space. How can I get around this?