diff --git a/PSOperations/Operation.swift b/PSOperations/Operation.swift
index deaa33b..a58d974 100644
--- a/PSOperations/Operation.swift
+++ b/PSOperations/Operation.swift
@@ -18,12 +18,18 @@ public typealias PSOperation = Operation
 open class Operation: Foundation.Operation {
 
     private static var psoperationContext = 0
-
+    
+#if swift(>=5.9)
+    public typealias CompletionBlock = @Sendable () -> Void
+#else
+    public typealias CompletionBlock = () -> Void
+#endif
+    
     /* The completionBlock property has unexpected behaviors such as executing twice and executing on unexpected threads. BlockObserver
      * executes in an expected manner.
      */
     @available(*, deprecated, message: "use BlockObserver completions instead")
-    override open var completionBlock: (() -> Void)? {
+    override open var completionBlock: CompletionBlock? {
         get {
             return nil
         }