diff --git a/Package.swift b/Package.swift
index 9c0c629..ef7d1be 100644
--- a/Package.swift
+++ b/Package.swift
@@ -27,7 +27,7 @@ let package = Package(
     .default(enabledTraits: ["UseSwiftCrypto"]),
   ],
   dependencies: [
-    .package(url: "https://github.com/apple/swift-crypto", from: "2.0.0"),
+    .package(url: "https://github.com/apple/swift-crypto", "1.0.0" ..< "4.0.0"),
     .package(url: "https://github.com/lovetodream/swift-blake2", from: "0.1.0")
   ],
   targets: [
@@ -44,5 +44,6 @@ let package = Package(
       name: "MinisignTests",
       dependencies: ["Minisign"]
     ),
-  ]
+  ],
+  swiftLanguageModes: [.v6]
 )
diff --git a/Package@swift-5.8.swift b/Package@swift-5.9.swift
similarity index 90%
rename from Package@swift-5.8.swift
rename to Package@swift-5.9.swift
index 46b4194..33d3fa9 100644
--- a/Package@swift-5.8.swift
+++ b/Package@swift-5.9.swift
@@ -1,4 +1,4 @@
-// swift-tools-version: 5.8
+// swift-tools-version: 5.9
 
 import PackageDescription
 
@@ -18,7 +18,7 @@ let package = Package(
     )
   ],
   dependencies: [
-    .package(url: "https://github.com/apple/swift-crypto", from: "2.0.0"),
+    .package(url: "https://github.com/apple/swift-crypto", "1.0.0" ..< "4.0.0"),
     .package(url: "https://github.com/lovetodream/swift-blake2", from: "0.1.0"),
   ],
   targets: [
diff --git a/Sources/Minisign/Minisign.swift b/Sources/Minisign/Minisign.swift
index bf40538..ecaa5b4 100644
--- a/Sources/Minisign/Minisign.swift
+++ b/Sources/Minisign/Minisign.swift
@@ -6,9 +6,9 @@ import BLAKE2
 import Foundation
 
 #if UseSwiftCrypto
-  import Crypto
+  @preconcurrency import Crypto
 #else
-  import CryptoKit
+  @preconcurrency import CryptoKit
 #endif
 
 public enum SignatureAlgorithm: Sendable, RawRepresentable {