Cannot visualize glm

[amazingoats]

When following along with your video on generalized mixed models in R, when I enter the code visualize(reduced, plot = "model", formula = progressed ~ class_size, data = d), it returns "Error in eval(predvars, data, env) : object 'class_id' not found." Everything else is identical, so I can't figure out what is going wrong, maybe an incompatible update?