Quiz lesson icon confuses users

The icon that indicates a lesson ends in a quiz is a checked square checkbox. However, this icon appears next to an empty round checkbox that indicates if the lesson is complete or not. We have had several users report that they find this confusing. Some users think they have completed the quiz because they see a checked checkbox.

A question mark icon like this would be more appropriate and less confusing: https://thenounproject.com/icon/question-5179459/.

Here is an example: