Petitioner-appellant Eugenio Lopez Rodriguez appeals from the district court's denial of his request for an evidentiary hearing and subsequent dismissal of his habeas corpus petition, 28 U.S.C. Sec. 2254. Our jurisdiction arises under 28 U.S.C. Secs. 1291 & 2253, and we affirm.

In an attempt to collaterally attack the presumptive voluntariness of his plea, see Blackledge v. Allison, 431 U.S. 63, 74, 97 S. Ct. 1621, 1629, 52 L. Ed. 2d 136 (1977), Mr. Lopez asserts by affidavit that the government breached a promise, undisclosed on the record of the plea proceedings, of an unsupervised conjugal visit. Although promises made by prosecuting attorneys "must be fulfilled to maintain the integrity of the plea," United States v. Hand, 913 F.2d 854, 856 (10th Cir.1990) (citing Santobello v. New York, 404 U.S. 257, 262, 92 S. Ct. 495, 499, 30 L. Ed. 2d 427 (1971)), only breaches of material promises will allow a court to conclude that a plea was involuntarily induced and thus constitutionally infirm. United States v. Pollard, 959 F.2d 1011, 1028 (D.C.Cir.), cert. denied, --- U.S. ----, 113 S. Ct. 322, 121 L. Ed. 2d 242 (1992). As in contract, the terms of a plea agreement and their relative materiality are evaluated by an objective standard. See McKenzie v. Risley, 801 F.2d 1519, 1526-27 (9th Cir.1986), vacated in part on other grounds, 842 F.2d 1525 (9th Cir.1988) (en banc). In light of the significant benefits Mr. Lopez did receive as a result of his plea agreement, including the avoidance of a possible death sentence, the alleged breach of a promise of a conjugal visit did not deprive the agreement of its voluntary character. Because Mr. Lopez has failed to "allege[ ] facts which, if proven, would entitle him to relief," Townsend v. Sain, 372 U.S. 293, 312, 83 S. Ct. 745, 757, 9 L. Ed. 2d 770 (1963), the district court did not err in denying his request for an evidentiary hearing and dismissing the petition.

AFFIRMED.