diff --git a/CotEditor/Sources/Pair.swift b/CotEditor/Sources/Pair.swift
index 2fc83282b..2658a88b2 100644
--- a/CotEditor/Sources/Pair.swift
+++ b/CotEditor/Sources/Pair.swift
@@ -8,7 +8,7 @@
 //
 //  ---------------------------------------------------------------------------
 //
-//  © 2016-2022 1024jp
+//  © 2016-2024 1024jp
 //
 //  Licensed under the Apache License, Version 2.0 (the "License");
 //  you may not use this file except in compliance with the License.
@@ -39,6 +39,7 @@ struct Pair<T> {
 
 extension Pair: Equatable where T: Equatable { }
 extension Pair: Hashable where T: Hashable { }
+extension Pair: Sendable where T: Sendable { }