Trouble with FastAPI, TestClient, and the debugger

I am working on a small-ish FastAPI application, and our tests are written using starlette.TestClient. This works well enough, but when I want to debug one of our test failures, I do the obvious – drop a breakpoint in the PyCharm debugger inside the FastAPI code; however, I cannot then get PyCharm to respect the breakpoint. Obviously, breakpoints inside the test code are respected; but those in the body of the application are not.

This seems like something I should be able to do. Am I missing something obvious? Calling the endpoints without running the debugger does not show the same errors, so.