KETHLEDGE, Circuit Judge. Undisputed in this case is that, in January 2016, the prosecutor in Amaury Villa’s case emailed Villa’s counsel, Donald Meier, with an offer to enter into a cooperation agreement with Villa. What the parties dispute is when Villa learned about that offer. The government says that Meier told Villa about the offer the day it was made. Villa says that he learned about that offer only years later, when he obtained the relevant portion of Meier’s case file. By then Villa had pending with the district court a motion for relief from sentence under 28 U.S.C. § 2255, which he promptly moved to amend with a claim based on Meier’s alleged omission. Villa attached two affidavits (including his own) in support of his motion to amend; the government attached an affidavit from Meier in opposition. Yet the district court summarily adopted the government’s view of the facts and denied Villa’s motion to amend as untimely. We vacate the court’s decision and remand for an evidentiary hearing.