A year after being fired by former Trump national security adviser Michael Flynn, lawyers at Covington & Burling revealed Thursday that they recently uncovered emails and handwritten notes that were “inadvertently” left out of a trove of records turned over last summer to his new defense counsel.

In a court filing, Flynn’s former lawyers at Covington said they had discovered the records as they prepared to respond to the retired Army general’s allegation that the firm provided him with ineffective counsel. Flynn has criticized Covington’s representation of him amid his bid to withdraw his 2017 guilty plea, in which he admitted to lying to the FBI about his past communications with the Russian ambassador to the U.S.