Using "mae" and "mape" metric in selecting the best regression tree in R

Question

I'm trying to select the best regression tree using the "mae" or the "mape" metrics, but doesn't seem to recognize it.

My try:

best_complexity <- select_best(tune_res, metric = "mae")

reg_tree_final <- finalize_workflow(reg_tree_wf, best_complexity)

reg_tree_final_fit <- fit(reg_tree_final, data = Boston_train)
reg_tree_final_fit

In the other hand, my code using the "rmse" metric i'ts working just fine. Any suggestion would be great!