Sam Dastyari - dual citizenship or not

This is what Sam said yesterday when attacking Trump:

“It’s so saddening that as an Australian senator, despite having taken every possible step to renounce my Iranian citizenship, I can not tell you with any certainty whether I would be allowed in the US today,” Senator Dastyari told Fairfax Media.

That implies he still retains Iranian citizenship as well as Australian. Unless I am missing something, he cannot be a member of Parliament.