Swiss National Bank chair Philipp Hildebrand resigned late on Monday over a controversial personal foreign currency trade undertaken by his wife.

Hildrebrand’s wife Kashya had switched SFr400,000 into dollars in mid August, just days before a Swiss National Bank intervention in the FX market.

Hildebrand said at a press conference after his resignation: “I came to the conclusion that it is not possible for me to deliver a definite proof that my wife requested the currency transaction without my knowledge. Unfortunately, mistakes were made around this transaction.”

Meanwhile, the bank has begun its search for a replacement. Vice Chairman Thomas Jordan, who has been with the Swiss National Bank almost five years, is said to take over temporarily, but may be confirmed by the government as the permanent replacement shortly after.