diff --git a/Package.swift b/Package.swift
index db38b79..e6913f6 100644
--- a/Package.swift
+++ b/Package.swift
@@ -1,4 +1,4 @@
-// swift-tools-version: 5.7
+// swift-tools-version: 6.0
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 
 import PackageDescription
diff --git a/Sources/LucaCLI/Commands/InstallCommand.swift b/Sources/LucaCLI/Commands/InstallCommand.swift
index c4561f6..4d23cb9 100644
--- a/Sources/LucaCLI/Commands/InstallCommand.swift
+++ b/Sources/LucaCLI/Commands/InstallCommand.swift
@@ -5,7 +5,7 @@ import Foundation
 import LucaCore
 import Yams
 
-extension ChecksumAlgorithm: @retroactive ExpressibleByArgument {}
+extension ChecksumAlgorithm: ExpressibleByArgument {}
 
 /// Installs the versions of tools specified by a YAML spec file.
 struct InstallCommand: AsyncParsableCommand {