The midfielder was dumped from victory over Juventus after a strop in the Europa League last week.
“He just has to prove that Inter are his team," De Boer shrugged.
“When he returns to us isn't a problem for me. He did something I couldn't accept, so he'll return to the squad when he can demonstrate his discipline."
De Boer also spoke of skipper Mauro Icardi.
“I'm very satisfied with what he's doing, he's our captain and he has to show every day that he deserves that role.
“He's doing that on a daily basis, both in training and in matches. I'm happy and he's doing great things, also very difficult things.
“I repeat: I'm pleased with him."