Can Mustafa challenge the government's post-amendment proof of conspiracy?

At the outset, we note that the conspiracy charged in Count Seven is alleged to have operated between approximately June 2000 (before 2339A's amendment) and December 19, 2001 (approximately six weeks after amendment). Mustafa did not raise any sufficiency challenge to the government's post-amendment proof of conspiracy in the district court and, indeed, did so on appeal only in response to an inquiry from this court. Now, however, he argues that the government failed to prove not only that the charged conspiracy existed after October 26, 2001, but also that a conspirator committed at least one post-amendment overt act in furtherance of the scheme. He maintains that review of this unpreserved argument is not limited to plain error, see United States v. Marcus, 560 U.S. 258, 262 (2010), because the government waived any challenge to a 2339A overt act requirement by its request for an overt act charge.