President-elect Donald Trump at one time repeatedly lambasted Hillary Clinton over her use of a private email server during her stint as secretary of state, but he isn’t exactly nailing communications either. A recent series of phone calls to foreign leaders shows that Trump has not mastered the art of the diplomatic phone call quite yet.

Most recently, on Friday, Trump took a phone call from Taiwan President Tsai Ing-wen, angering officials in China and fumbling years of diplomatic practice on the part of the United States, specifically its “one China principle,” which acknowledges that there is only one state called China despite the existence of two governments that claim to represent China. Trump, however claimed on Twitter that, “The President of Taiwan CALLED ME,” and Chinese Foreign Minister Wang Yi blamed Taiwan for the conversation. “This is just the Taiwan side engaging in a petty action, and cannot change the ‘one China’ structure already formed by the international community,” Wang said Saturday, according to Reuters. However, Alex Huang, a spokesman for Tsai, also told Reuters: “Of course both sides agreed ahead of time before making contact.