diff --git a/AMSMB2/AMSMB2.swift b/AMSMB2/AMSMB2.swift
index 71f02e4..cf0d86b 100644
--- a/AMSMB2/AMSMB2.swift
+++ b/AMSMB2/AMSMB2.swift
@@ -16,7 +16,7 @@ public typealias AMSMB2 = SMB2Manager
 /// Implements SMB2 File operations.
 @objc(AMSMB2Manager)
 public class SMB2Manager: NSObject, NSSecureCoding, Codable, NSCopying, CustomReflectable, @unchecked Sendable {
-    public typealias SimpleCompletionHandler = (@Sendable (_ error: Error?) -> Void)?
+    public typealias SimpleCompletionHandler = (@Sendable (_ error: (any Error)?) -> Void)?
     public typealias ReadProgressHandler = (@Sendable (_ bytes: Int64, _ total: Int64) -> Bool)?
     public typealias WriteProgressHandler = (@Sendable (_ bytes: Int64) -> Bool)?
     fileprivate typealias CopyProgressHandler = (@Sendable
@@ -181,7 +181,7 @@ public class SMB2Manager: NSObject, NSSecureCoding, Codable, NSCopying, CustomRe
         case user, password, timeout
     }
 
-    public required init(from decoder: Decoder) throws {
+    public required init(from decoder: any Decoder) throws {
         let container = try decoder.container(keyedBy: CodingKeys.self)
         let url = try container.decode(URL.self, forKey: .url)
         guard url.scheme?.lowercased() == "smb" else {
@@ -203,7 +203,7 @@ public class SMB2Manager: NSObject, NSSecureCoding, Codable, NSCopying, CustomRe
         super.init()
     }
 
-    open func encode(to encoder: Encoder) throws {
+    open func encode(to encoder: any Encoder) throws {
         var container = encoder.container(keyedBy: CodingKeys.self)
         try container.encode(url, forKey: .url)
         try container.encode(_domain, forKey: .domain)
@@ -346,7 +346,7 @@ public class SMB2Manager: NSObject, NSSecureCoding, Codable, NSCopying, CustomRe
      */
     open func listShares(
         enumerateHidden: Bool = false,
-        completionHandler: @Sendable @escaping (_ result: Result<[(name: String, comment: String)], Error>) -> Void
+        completionHandler: @Sendable @escaping (_ result: Result<[(name: String, comment: String)], any Error>) -> Void
     ) {
         // Connecting to Interprocess Communication share
         with(shareName: "IPC$", encrypted: false, completionHandler: completionHandler) { context in
@@ -377,7 +377,7 @@ public class SMB2Manager: NSObject, NSSecureCoding, Codable, NSCopying, CustomRe
     /// Only for test case coverage
     func _swift_listShares(
         enumerateHidden: Bool = false,
-        completionHandler: @Sendable @escaping (_ result: Result<[(name: String, comment: String)], Error>) -> Void
+        completionHandler: @Sendable @escaping (_ result: Result<[(name: String, comment: String)], any Error>) -> Void
     ) {
         with(shareName: "IPC$", encrypted: false, completionHandler: completionHandler) { context in
             try context.shareEnumSwift().map(enumerateHidden: enumerateHidden)
@@ -406,7 +406,7 @@ public class SMB2Manager: NSObject, NSSecureCoding, Codable, NSCopying, CustomRe
      */
     open func contentsOfDirectory(
         atPath path: String, recursive: Bool = false,
-        completionHandler: @Sendable @escaping (_ result: Result<[[URLResourceKey: Any]], Error>) -> Void
+        completionHandler: @Sendable @escaping (_ result: Result<[[URLResourceKey: Any]], any Error>) -> Void
     ) {
         with(completionHandler: completionHandler) { context in
             try self.listDirectory(context: context, path: path, recursive: recursive)
@@ -443,7 +443,7 @@ public class SMB2Manager: NSObject, NSSecureCoding, Codable, NSCopying, CustomRe
      */
     open func attributesOfFileSystem(
         forPath path: String,
-        completionHandler: @Sendable @escaping (_ result: Result<[FileAttributeKey: Any], Error>) -> Void
+        completionHandler: @Sendable @escaping (_ result: Result<[FileAttributeKey: Any], any Error>) -> Void
     ) {
         with(completionHandler: completionHandler) { context in
             // This exactly matches implementation of Swift Foundation.
@@ -487,7 +487,7 @@ public class SMB2Manager: NSObject, NSSecureCoding, Codable, NSCopying, CustomRe
      */
     open func attributesOfItem(
         atPath path: String,
-        completionHandler: @Sendable @escaping (_ result: Result<[URLResourceKey: Any], Error>) -> Void
+        completionHandler: @Sendable @escaping (_ result: Result<[URLResourceKey: Any], any Error>) -> Void
     ) {
         with(completionHandler: completionHandler) { context in
             let stat = try context.stat(path)
@@ -606,7 +606,7 @@ public class SMB2Manager: NSObject, NSSecureCoding, Codable, NSCopying, CustomRe
      */
     open func destinationOfSymbolicLink(
         atPath path: String,
-        completionHandler: @Sendable @escaping (_ result: Result<String, Error>) -> Void
+        completionHandler: @Sendable @escaping (_ result: Result<String, any Error>) -> Void
     ) {
         with(completionHandler: completionHandler) { context in
             try context.readlink(path)
@@ -834,7 +834,7 @@ public class SMB2Manager: NSObject, NSSecureCoding, Codable, NSCopying, CustomRe
     open func contents<R: RangeExpression>(
         atPath path: String, range: R? = Range<UInt64>?.none,
         progress: ReadProgressHandler,
-        completionHandler: @Sendable @escaping (_ result: Result<Data, Error>) -> Void
+        completionHandler: @Sendable @escaping (_ result: Result<Data, any Error>) -> Void
     ) where R.Bound: FixedWidthInteger {
         let range = range?.int64Range ?? 0..<Int64.max
         with(completionHandler: completionHandler) { context in
@@ -943,7 +943,7 @@ public class SMB2Manager: NSObject, NSSecureCoding, Codable, NSCopying, CustomRe
      */
     open func contents<R: RangeExpression>(
         atPath path: String, range: R? = Range<UInt64>?.none
-    ) -> AsyncThrowingStream<Data, Error> where R.Bound: FixedWidthInteger {
+    ) -> AsyncThrowingStream<Data, any Error> where R.Bound: FixedWidthInteger {
         let range = range?.int64Range ?? 0..<Int64.max
         let (result, continuation) = AsyncThrowingStream.makeStream(of: Data.self, bufferingPolicy: .unbounded)
         
@@ -1438,7 +1438,7 @@ extension SMB2Manager {
     }
 
     private func with<T>(
-        completionHandler: @Sendable @escaping (Result<T, Error>) -> Void,
+        completionHandler: @Sendable @escaping (Result<T, any Error>) -> Void,
         handler: @Sendable @escaping (_ context: SMB2Context) throws -> T
     ) {
         queue {
@@ -1451,7 +1451,7 @@ extension SMB2Manager {
     }
 
     private func with<T>(
-        shareName: String, encrypted: Bool, completionHandler: @Sendable @escaping (Result<T, Error>) -> Void,
+        shareName: String, encrypted: Bool, completionHandler: @Sendable @escaping (Result<T, any Error>) -> Void,
         handler: @Sendable @escaping (_ context: SMB2Context) throws -> T
     ) {
         queue {
diff --git a/AMSMB2/Context.swift b/AMSMB2/Context.swift
index 5484bd9..6103916 100644
--- a/AMSMB2/Context.swift
+++ b/AMSMB2/Context.swift
@@ -375,7 +375,7 @@ extension SMB2Context {
         try withThreadSafeContext { context -> (Int32, DataType) in
             var cb = CBData()
             var resultData: DataType?
-            var dataHandlerError: Error?
+            var dataHandlerError: (any Error)?
             cb.dataHandler = { ptr in
                 do {
                     resultData = try dataHandler(self, ptr)
@@ -413,7 +413,7 @@ extension SMB2Context {
         try withThreadSafeContext { context -> (UInt32, DataType) in
             var cb = CBData()
             var resultData: DataType?
-            var dataHandlerError: Error?
+            var dataHandlerError: (any Error)?
             cb.dataHandler = { ptr in
                 do {
                     resultData = try dataHandler(self, ptr)
diff --git a/AMSMB2/Extensions.swift b/AMSMB2/Extensions.swift
index 8c9687e..088afae 100644
--- a/AMSMB2/Extensions.swift
+++ b/AMSMB2/Extensions.swift
@@ -270,7 +270,7 @@ extension OutputStream {
     }
 }
 
-func asyncHandler(_ continuation: CheckedContinuation<Void, Error>) -> @Sendable (_ error: Error?) -> Void {
+func asyncHandler(_ continuation: CheckedContinuation<Void, any Error>) -> @Sendable (_ error: (any Error)?) -> Void {
     { error in
         if let error = error {
             continuation.resume(throwing: error)
@@ -280,7 +280,7 @@ func asyncHandler(_ continuation: CheckedContinuation<Void, Error>) -> @Sendable
     }
 }
 
-func asyncHandler<T>(_ continuation: CheckedContinuation<T, Error>) -> @Sendable (Result<T, Error>) -> Void {
+func asyncHandler<T>(_ continuation: CheckedContinuation<T, any Error>) -> @Sendable (Result<T, any Error>) -> Void {
     { result in
         continuation.resume(with: result)
     }
diff --git a/AMSMB2/ObjCCompat.swift b/AMSMB2/ObjCCompat.swift
index 27e706b..f66fd54 100644
--- a/AMSMB2/ObjCCompat.swift
+++ b/AMSMB2/ObjCCompat.swift
@@ -20,7 +20,7 @@ extension SMB2Manager {
      */
     @available(swift, obsoleted: 1.0)
     @objc(connectShareWithName:completionHandler:)
-    open func __connectShare(name: String, completionHandler: @Sendable @escaping (_ error: Error?) -> Void) {
+    open func __connectShare(name: String, completionHandler: @Sendable @escaping (_ error: (any Error)?) -> Void) {
         connectShare(name: name, completionHandler: completionHandler)
     }
 
@@ -61,7 +61,7 @@ extension SMB2Manager {
     @available(swift, obsoleted: 1.0)
     @objc(listSharesWithCompletionHandler:)
     public func __listShares(
-        completionHandler: @Sendable @escaping (_ names: [String], _ comments: [String], _ error: Error?) -> Void
+        completionHandler: @Sendable @escaping (_ names: [String], _ comments: [String], _ error: (any Error)?) -> Void
     ) {
         listShares(enumerateHidden: false) { result in
             switch result {
@@ -88,7 +88,7 @@ extension SMB2Manager {
     @objc(listSharesWithEnumerateHidden:completionHandler:)
     public func __listShares(
         enumerateHidden: Bool,
-        completionHandler: @Sendable @escaping (_ names: [String], _ comments: [String], _ error: Error?) -> Void
+        completionHandler: @Sendable @escaping (_ names: [String], _ comments: [String], _ error: (any Error)?) -> Void
     ) {
         listShares(enumerateHidden: enumerateHidden) { result in
             switch result {
@@ -114,7 +114,7 @@ extension SMB2Manager {
     @objc(contentsOfDirectoryAtPath:recursive:completionHandler:)
     public func __contentsOfDirectory(
         atPath path: String, recursive: Bool = false,
-        completionHandler: @Sendable @escaping (_ contents: [[URLResourceKey: Any]]?, _ error: Error?) -> Void
+        completionHandler: @Sendable @escaping (_ contents: [[URLResourceKey: Any]]?, _ error: (any Error)?) -> Void
     ) {
         contentsOfDirectory(
             atPath: path, recursive: recursive, completionHandler: convert(completionHandler)
@@ -135,7 +135,7 @@ extension SMB2Manager {
     @objc(attributesOfFileSystemForPath:completionHandler:)
     public func __attributesOfFileSystem(
         forPath path: String,
-        completionHandler: @Sendable @escaping (_ attributes: [FileAttributeKey: Any]?, _ error: Error?) -> Void
+        completionHandler: @Sendable @escaping (_ attributes: [FileAttributeKey: Any]?, _ error: (any Error)?) -> Void
     ) {
         attributesOfFileSystem(forPath: path, completionHandler: convert(completionHandler))
     }
@@ -153,7 +153,7 @@ extension SMB2Manager {
     @objc(attributesOfItemAtPath:completionHandler:)
     public func __attributesOfItem(
         atPath path: String,
-        completionHandler: @Sendable @escaping (_ file: [URLResourceKey: Any]?, _ error: Error?) -> Void
+        completionHandler: @Sendable @escaping (_ file: [URLResourceKey: Any]?, _ error: (any Error)?) -> Void
     ) {
         attributesOfItem(atPath: path, completionHandler: convert(completionHandler))
     }
@@ -172,7 +172,7 @@ extension SMB2Manager {
     @objc(destinationOfSymbolicLinkAtPath:completionHandler:)
     open func __destinationOfSymbolicLink(
         atPath path: String,
-        completionHandler: @Sendable @escaping (_ destinationPath: String?, _ error: Error?) -> Void
+        completionHandler: @Sendable @escaping (_ destinationPath: String?, _ error: (any Error)?) -> Void
     ) {
         destinationOfSymbolicLink(atPath: path, completionHandler: convert(completionHandler))
     }
@@ -200,7 +200,7 @@ extension SMB2Manager {
     @objc(contentsAtPath:fromOffset:toLength:progress:completionHandler:)
     open func __contents(
         atPath path: String, offset: Int64 = 0, length: Int = -1, progress: ReadProgressHandler,
-        completionHandler: @Sendable @escaping (_ contents: Data?, _ error: Error?) -> Void
+        completionHandler: @Sendable @escaping (_ contents: Data?, _ error: (any Error)?) -> Void
     ) {
         guard offset >= 0 else {
             let error = POSIXError(.EINVAL, description: "Invalid content offset.")
@@ -239,8 +239,8 @@ extension SMB2Manager {
 }
 
 extension SMB2Manager {
-    private func convert<T>(_ resultCompletion: @Sendable @escaping (T?, Error?) -> Void) -> (
-        @Sendable (Result<T, Error>) -> Void
+    private func convert<T>(_ resultCompletion: @Sendable @escaping (T?, (any Error)?) -> Void) -> (
+        @Sendable (Result<T, any Error>) -> Void
     ) {
         { result in
             switch result {
diff --git a/AMSMB2Tests/SMB2ManagerTests.swift b/AMSMB2Tests/SMB2ManagerTests.swift
index 29a717e..f1e82d5 100644
--- a/AMSMB2Tests/SMB2ManagerTests.swift
+++ b/AMSMB2Tests/SMB2ManagerTests.swift
@@ -386,6 +386,59 @@ class SMB2ManagerTests: XCTestCase {
         XCTAssert(outputStream.streamStatus == .closed)
         XCTAssert(FileManager.default.contentsEqual(atPath: url.path, andPath: dlURL.path))
     }
+    
+    func testSimultaneousUpload() async throws {
+        let redownload = false
+        let fileNums = 5
+        let files = (1...fileNums).map { "uploadsimtest\($0).dat" }
+        let urls = (1...fileNums).map {
+            let size: Int = random(max: 0xf00000)
+            print(#function, "test size \($0):", size)
+            return self.dummyFile(size: size)
+        }
+        
+        let smb = SMB2Manager(url: server, credential: credential)!
+        try await smb.connectShare(name: share, encrypted: encrypted)
+        
+        addTeardownBlock {
+            try? urls.forEach(FileManager.default.removeItem(at:))
+            try? urls
+                .map { $0.appendingPathExtension("download") }
+                .forEach(FileManager.default.removeItem(at:))
+            await withTaskGroup(of: Void.self) { group in
+                for file in files {
+                    group.addTask{
+                        try? await smb.removeFile(atPath: file)
+                    }
+                }
+                await group.waitForAll()
+            }
+            for file in files {
+                try? await smb.removeFile(atPath: file)
+            }
+        }
+        
+        try await withThrowingTaskGroup(of: Void.self) { group in
+            for (file, url) in zip(files, urls) {
+                group.addTask{
+                    try await smb.uploadItem(at: url, toPath: file, progress: nil)
+                }
+            }
+            
+            try await group.waitForAll()
+        }
+        
+        guard redownload else { return }
+        try await withThrowingTaskGroup(of: Void.self) { group in
+            for (file, url) in zip(files, urls) {
+                group.addTask{
+                    try await smb.downloadItem(atPath: file, to: url.appendingPathExtension("download"), progress: nil)
+                }
+            }
+            
+            try await group.waitForAll()
+        }
+    }
 
     func testTruncate() async throws {
         let smb = SMB2Manager(url: server, credential: credential)!