diff --git a/Package.swift b/Package.swift
index d4fb083..42542a1 100644
--- a/Package.swift
+++ b/Package.swift
@@ -54,7 +54,8 @@ let package = Package(
                 .target(name: "Subprocess")
             ]
         )
-    ]
+    ],
+    swiftLanguageVersions: [.v5, .version("6")]
 )
 
 for target in package.targets {
@@ -65,60 +66,24 @@ for target in package.targets {
     // as upcoming features will result in a compiler error. Currently in the
     // latest 5.10 compiler this doesn't happen, the compiler ignores it.
     //
-    // If the situation does change and enabling default language features
-    // does result in an error in future versions we attempt to guard against
-    // this by using the hasFeature(x) compiler directive to see if we have a
-    // feature already, or if we can enable it. It's safe to enable features
-    // that don't exist in older compiler versions as the compiler will ignore
-    // features it doesn't have implemented.
-    
-    // swift 6
-    #if !hasFeature(ConciseMagicFile)
-    swiftSettings.append(.enableUpcomingFeature("ConciseMagicFile"))
-    #endif
-
-    #if !hasFeature(ForwardTrailingClosures)
-    swiftSettings.append(.enableUpcomingFeature("ForwardTrailingClosures"))
-    #endif
-
-    #if !hasFeature(StrictConcurrency)
-    swiftSettings.append(.enableUpcomingFeature("StrictConcurrency"))
-    // StrictConcurrency is under experimental features in Swift <=5.10 contrary to some posts and documentation
-    swiftSettings.append(.enableExperimentalFeature("StrictConcurrency"))
-    #endif
-
-    #if !hasFeature(BareSlashRegexLiterals)
-    swiftSettings.append(.enableUpcomingFeature("BareSlashRegexLiterals"))
-    #endif
-
-    #if !hasFeature(ImplicitOpenExistentials)
-    swiftSettings.append(.enableUpcomingFeature("ImplicitOpenExistentials"))
-    #endif
-
-    #if !hasFeature(ImportObjcForwardDeclarations)
-    swiftSettings.append(.enableUpcomingFeature("ImportObjcForwardDeclarations"))
-    #endif
-
-    #if !hasFeature(DisableOutwardActorInference)
-    swiftSettings.append(.enableUpcomingFeature("DisableOutwardActorInference"))
-    #endif
-
-    #if !hasFeature(InternalImportsByDefault)
-    swiftSettings.append(.enableUpcomingFeature("InternalImportsByDefault"))
-    #endif
-    
-    #if !hasFeature(IsolatedDefaultValues)
-    swiftSettings.append(.enableUpcomingFeature("IsolatedDefaultValues"))
-    #endif
-    
-    #if !hasFeature(GlobalConcurrency)
-    swiftSettings.append(.enableUpcomingFeature("GlobalConcurrency"))
-    #endif
+    // The Swift 6 compiler on the other hand does emit errors when features
+    // are enabled. Unfortunately it appears that the preprocessor
+    // !hasFeature(xxx) cannot be used to test for this situation nor does
+    // #if swift(<6) guard against this. There must be some sort of magic
+    // used that is special for compiling the Package.swift manifest.
+    // Instead a versioned Package.swift can be used (e.g. Package@swift-5.10.swift)
+    // and the implemented now default features can be removed in Package.swift.
+    //
+    // Or you can just delete the Swift 6 features that are enabled instead of
+    // creating another manifest file and test to see if building under Swift 5
+    // still works (it should almost always work).
+    //
+    // It's still safe to enable features that don't exist in older compiler
+    // versions as the compiler will ignore features it doesn't have implemented.
 
     // swift 7
-    #if !hasFeature(ExistentialAny)
     swiftSettings.append(.enableUpcomingFeature("ExistentialAny"))
-    #endif
+    swiftSettings.append(.enableUpcomingFeature("InternalImportsByDefault"))
     
     target.swiftSettings = swiftSettings
 }
diff --git a/Sources/Subprocess/AsyncSequence+Additions.swift b/Sources/Subprocess/AsyncSequence+Additions.swift
index f39bd85..f236d4a 100644
--- a/Sources/Subprocess/AsyncSequence+Additions.swift
+++ b/Sources/Subprocess/AsyncSequence+Additions.swift
@@ -25,7 +25,11 @@
 //  SOFTWARE.
 //
 
+#if swift(>=6.0)
+public import Foundation
+#else
 import Foundation
+#endif
 
 extension AsyncSequence {
     /// Returns a sequence of all the elements.
diff --git a/Sources/Subprocess/AsyncStream+Yield.swift b/Sources/Subprocess/AsyncStream+Yield.swift
index 383edba..e69b83d 100644
--- a/Sources/Subprocess/AsyncStream+Yield.swift
+++ b/Sources/Subprocess/AsyncStream+Yield.swift
@@ -25,7 +25,11 @@
 //  SOFTWARE.
 //
 
+#if swift(>=6.0)
+public import Foundation
+#else
 import Foundation
+#endif
 
 extension AsyncStream.Continuation where Element == UInt8 {
     /// Resume the task awaiting the next iteration point by having it return
diff --git a/Sources/Subprocess/Input.swift b/Sources/Subprocess/Input.swift
index 1598ae4..340dbbc 100644
--- a/Sources/Subprocess/Input.swift
+++ b/Sources/Subprocess/Input.swift
@@ -24,7 +24,12 @@
 //  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 //  SOFTWARE.
 //
+
+#if swift(>=6.0)
+public import Foundation
+#else
 import Foundation
+#endif
 
 /// Interface representing input to the process
 public struct Input {
diff --git a/Sources/Subprocess/Pipe+AsyncBytes.swift b/Sources/Subprocess/Pipe+AsyncBytes.swift
index 78cebd7..34342fc 100644
--- a/Sources/Subprocess/Pipe+AsyncBytes.swift
+++ b/Sources/Subprocess/Pipe+AsyncBytes.swift
@@ -25,7 +25,11 @@
 //  SOFTWARE.
 //
 
+#if swift(>=6.0)
+public import Foundation
+#else
 import Foundation
+#endif
 
 // `FileHandle.AsyncBytes` has a bug that can block reading of stdout when also reading stderr.
 // We can avoid this problem if we create independent handlers.
diff --git a/Sources/Subprocess/Shell.swift b/Sources/Subprocess/Shell.swift
index ebf8fd0..04eb85b 100644
--- a/Sources/Subprocess/Shell.swift
+++ b/Sources/Subprocess/Shell.swift
@@ -25,7 +25,11 @@
 //  SOFTWARE.
 //
 
+#if swift(>=6.0)
+public import Foundation
+#else
 import Foundation
+#endif
 
 /// Class used for synchronous process execution
 @available(*, deprecated, message: "Use Swift Concurrency methods instead which are part of the Subprocess class")
diff --git a/Sources/Subprocess/Subprocess.swift b/Sources/Subprocess/Subprocess.swift
index 1784157..7060b31 100644
--- a/Sources/Subprocess/Subprocess.swift
+++ b/Sources/Subprocess/Subprocess.swift
@@ -25,8 +25,13 @@
 //  SOFTWARE.
 //
 
+#if swift(>=6.0)
+public import Foundation
+public import Combine
+#else
 import Foundation
 import Combine
+#endif
 
 /// Class used for asynchronous process execution
 public class Subprocess: @unchecked Sendable {
diff --git a/Sources/Subprocess/SubprocessDependencyBuilder.swift b/Sources/Subprocess/SubprocessDependencyBuilder.swift
index df23179..f924753 100644
--- a/Sources/Subprocess/SubprocessDependencyBuilder.swift
+++ b/Sources/Subprocess/SubprocessDependencyBuilder.swift
@@ -25,7 +25,11 @@
 //  SOFTWARE.
 //
 
+#if swift(>=6.0)
+public import Foundation
+#else
 import Foundation
+#endif
 
 /// Protocol call used for dependency injection
 public protocol SubprocessDependencyFactory {
diff --git a/Sources/SubprocessMocks/MockOutput.swift b/Sources/SubprocessMocks/MockOutput.swift
index 79b911c..aa9bdc0 100644
--- a/Sources/SubprocessMocks/MockOutput.swift
+++ b/Sources/SubprocessMocks/MockOutput.swift
@@ -25,7 +25,11 @@
 //  SOFTWARE.
 //
 
+#if swift(>=6.0)
+public import Foundation
+#else
 import Foundation
+#endif
 
 /// A way to supply data to mock methods
 public protocol MockOutput: Sendable {
diff --git a/Sources/SubprocessMocks/MockProcess.swift b/Sources/SubprocessMocks/MockProcess.swift
index f524504..22db9e9 100644
--- a/Sources/SubprocessMocks/MockProcess.swift
+++ b/Sources/SubprocessMocks/MockProcess.swift
@@ -25,10 +25,12 @@
 //  SOFTWARE.
 //
 
+#if swift(>=6.0)
+public import Foundation
+#else
 import Foundation
-#if !COCOA_PODS
-import Subprocess
 #endif
+import Subprocess
 
 /// Interface used for mocking a process
 public struct MockProcess: Sendable {
@@ -66,7 +68,7 @@ public struct MockProcess: Sendable {
 }
 
 /// Subclass of `Process` used for mocking
-open class MockProcessReference: Process {
+open class MockProcessReference: Process, @unchecked Sendable {
     /// Context information and values used for overriden properties
     public struct Context {
 
diff --git a/Sources/SubprocessMocks/MockShell.swift b/Sources/SubprocessMocks/MockShell.swift
index c716e0b..571fec1 100644
--- a/Sources/SubprocessMocks/MockShell.swift
+++ b/Sources/SubprocessMocks/MockShell.swift
@@ -25,8 +25,11 @@
 //  SOFTWARE.
 //
 
+#if swift(>=6.0)
+public import Foundation
+public import Subprocess
+#else
 import Foundation
-#if !COCOA_PODS
 import Subprocess
 #endif
 
diff --git a/Sources/SubprocessMocks/MockSubprocess.swift b/Sources/SubprocessMocks/MockSubprocess.swift
index 3e32242..f3c989e 100644
--- a/Sources/SubprocessMocks/MockSubprocess.swift
+++ b/Sources/SubprocessMocks/MockSubprocess.swift
@@ -25,9 +25,13 @@
 //  SOFTWARE.
 //
 
+#if swift(>=6.0)
+public import Foundation
+public import Combine
+public import Subprocess
+#else
 import Foundation
 import Combine
-#if !COCOA_PODS
 import Subprocess
 #endif
 
diff --git a/Sources/SubprocessMocks/MockSubprocessDependencyBuilder.swift b/Sources/SubprocessMocks/MockSubprocessDependencyBuilder.swift
index ded6da8..1a61b6a 100644
--- a/Sources/SubprocessMocks/MockSubprocessDependencyBuilder.swift
+++ b/Sources/SubprocessMocks/MockSubprocessDependencyBuilder.swift
@@ -25,10 +25,12 @@
 //  SOFTWARE.
 //
 
+#if swift(>=6.0)
+public import Foundation
+#else
 import Foundation
-#if !COCOA_PODS
-import Subprocess
 #endif
+import Subprocess
 
 /// Error representing a failed call to Subprocess.expect or Shell.expect
 public struct ExpectationError: Error {
@@ -66,11 +68,11 @@ public extension SubprocessMockObject {
     static func reset() { MockSubprocessDependencyBuilder.shared.reset() }
 }
 
-public class MockFileHandle: FileHandle {
+public class MockFileHandle: FileHandle, @unchecked Sendable {
     public var url: URL?
 }
 
-public final class MockPipe: Pipe {
+public final class MockPipe: Pipe, @unchecked Sendable {
     private static let queue = DispatchQueue(label: "\(MockPipe.self)")
     private var _data: Data?
     public var data: Data? {