Defendant claims that the sentencing court should not have counted his 1997 conviction as a second violent felony conviction because it was allegedly obtained in violation of his constitutional right to effective counsel, in that counsel failed to seek youthful offender treatment. Since defendant is not challenging the substantive legality of his sentence, but asserting a procedural defect that can be waived ( see People v Samms, 95 NY2d 52, 56-58; People v Abruzzese, 30 AD3d 219, 220, lv denied 7 NY3d 784 [2006]), his valid waiver of his right to appeal forecloses that claim. Further, because he failed to challenge the constitutionality of the 1997 conviction when it was counted as a predicate conviction in 2004, or demonstrate good cause for such failure, he waived any future challenge to the 1997 conviction's constitutionality for sentence enhancement purposes ( see People v Crawford, 204 AD2d 203, lv denied 84 NY2d 906). We also reject defendant's claim on the merits.