Which is correct: の or を + 勉強に


I recently see this sentence:

> 日本へ美術の勉強に行きます

Previous lesson, I learnt that to express "to learn something", we use the
pattern:

> N (The subject to learn) + を + 勉強する

But the first sentence uses の instead.

Is it a typo or is there anything wrong with my understanding here?

