[xcode] suppress build warning
diff --git a/picotls.xcodeproj/project.pbxproj b/picotls.xcodeproj/project.pbxproj
index a496cb1..92b5954 100644
--- a/picotls.xcodeproj/project.pbxproj
+++ b/picotls.xcodeproj/project.pbxproj
@@ -801,7 +801,7 @@
 		106530AA1D9985E0005B2C60 /* Project object */ = {
 			isa = PBXProject;
 			attributes = {
-				LastUpgradeCheck = 0830;
+				LastUpgradeCheck = 1320;
 				ORGANIZATIONNAME = "DeNA Co., Ltd.";
 				TargetAttributes = {
 					106530CB1D9B3D45005B2C60 = {