I have an old application that uses Web-To-Lead. I'm updating it to use the REST API. We have a bunch of assignment rules set up for Leads. When we create a lead through Web-To-Lead, the Lead is assigned according to our assignment rules. However, when we create a Lead through the REST API, the assignment rules are completely ignored, and the Lead is assigned to the account whose credentials we used to authenticate through OAuth. This has slowed our sales team to a crawl, because now they have to assign leads by hand.

Any ideas how to fix this?