diff --git a/Package@swift-5.8.swift b/Package@swift-5.8.swift
index 4306ab956..fb860aff1 100644
--- a/Package@swift-5.8.swift
+++ b/Package@swift-5.8.swift
@@ -138,3 +138,17 @@ package.targets.append(contentsOf: [
     path: "Tools/changelog-authors"),
 ])
 #endif
+
+for target in package.targets {
+  switch target.type {
+  case .regular, .test, .executable:
+    var settings = target.swiftSettings ?? []
+    // https://github.com/swiftlang/swift-evolution/blob/main/proposals/0444-member-import-visibility.md
+    settings.append(.enableUpcomingFeature("MemberImportVisibility"))
+    target.swiftSettings = settings
+  case .macro, .plugin, .system, .binary:
+    break  // not applicable
+  @unknown default:
+    break  // we don't know what to do here, do nothing
+  }
+}
diff --git a/Sources/ArgumentParser/Completions/BashCompletionsGenerator.swift b/Sources/ArgumentParser/Completions/BashCompletionsGenerator.swift
index 4f7bd8425..85da31704 100644
--- a/Sources/ArgumentParser/Completions/BashCompletionsGenerator.swift
+++ b/Sources/ArgumentParser/Completions/BashCompletionsGenerator.swift
@@ -9,7 +9,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 internal import ArgumentParserToolInfo
 #else
 import ArgumentParserToolInfo
diff --git a/Sources/ArgumentParser/Completions/CompletionsGenerator.swift b/Sources/ArgumentParser/Completions/CompletionsGenerator.swift
index d196d00be..87e3932a0 100644
--- a/Sources/ArgumentParser/Completions/CompletionsGenerator.swift
+++ b/Sources/ArgumentParser/Completions/CompletionsGenerator.swift
@@ -9,10 +9,12 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 internal import ArgumentParserToolInfo
+internal import Foundation
 #else
 import ArgumentParserToolInfo
+import Foundation
 #endif
 
 /// A shell for which the parser can generate a completion script.
diff --git a/Sources/ArgumentParser/Completions/FishCompletionsGenerator.swift b/Sources/ArgumentParser/Completions/FishCompletionsGenerator.swift
index 3a722a8e6..549fdf846 100644
--- a/Sources/ArgumentParser/Completions/FishCompletionsGenerator.swift
+++ b/Sources/ArgumentParser/Completions/FishCompletionsGenerator.swift
@@ -9,10 +9,12 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 internal import ArgumentParserToolInfo
+internal import Foundation
 #else
 import ArgumentParserToolInfo
+import Foundation
 #endif
 
 extension ToolInfoV0 {
diff --git a/Sources/ArgumentParser/Completions/ZshCompletionsGenerator.swift b/Sources/ArgumentParser/Completions/ZshCompletionsGenerator.swift
index 60296aa24..4ed8c90cf 100644
--- a/Sources/ArgumentParser/Completions/ZshCompletionsGenerator.swift
+++ b/Sources/ArgumentParser/Completions/ZshCompletionsGenerator.swift
@@ -9,10 +9,12 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 internal import ArgumentParserToolInfo
+internal import Foundation
 #else
 import ArgumentParserToolInfo
+import Foundation
 #endif
 
 extension ToolInfoV0 {
diff --git a/Sources/ArgumentParser/Parsable Types/ParsableArguments.swift b/Sources/ArgumentParser/Parsable Types/ParsableArguments.swift
index 1154d6278..6eb0d5483 100644
--- a/Sources/ArgumentParser/Parsable Types/ParsableArguments.swift	
+++ b/Sources/ArgumentParser/Parsable Types/ParsableArguments.swift	
@@ -9,6 +9,12 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if compiler(>=6.0)
+internal import Foundation
+#else
+import Foundation
+#endif
+
 /// A type that can be parsed from a program's command-line arguments.
 ///
 /// When you implement a `ParsableArguments` type, all properties must be declared with
diff --git a/Sources/ArgumentParser/Parsing/CommandParser.swift b/Sources/ArgumentParser/Parsing/CommandParser.swift
index 3f2f08ccd..e4b42f440 100644
--- a/Sources/ArgumentParser/Parsing/CommandParser.swift
+++ b/Sources/ArgumentParser/Parsing/CommandParser.swift
@@ -9,7 +9,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 #if canImport(Dispatch)
 @preconcurrency private import class Dispatch.DispatchSemaphore
 #endif
diff --git a/Sources/ArgumentParser/Usage/DumpHelpGenerator.swift b/Sources/ArgumentParser/Usage/DumpHelpGenerator.swift
index 1dbd28fdf..895b27a6d 100644
--- a/Sources/ArgumentParser/Usage/DumpHelpGenerator.swift
+++ b/Sources/ArgumentParser/Usage/DumpHelpGenerator.swift
@@ -9,7 +9,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 internal import ArgumentParserToolInfo
 internal import class Foundation.JSONEncoder
 #else
diff --git a/Sources/ArgumentParser/Usage/MessageInfo.swift b/Sources/ArgumentParser/Usage/MessageInfo.swift
index 4e42b4601..7d0c8a2c3 100644
--- a/Sources/ArgumentParser/Usage/MessageInfo.swift
+++ b/Sources/ArgumentParser/Usage/MessageInfo.swift
@@ -9,7 +9,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 internal import protocol Foundation.LocalizedError
 internal import class Foundation.NSError
 #else
diff --git a/Sources/ArgumentParser/Usage/UsageGenerator.swift b/Sources/ArgumentParser/Usage/UsageGenerator.swift
index 9c628c0cc..f73d80d1f 100644
--- a/Sources/ArgumentParser/Usage/UsageGenerator.swift
+++ b/Sources/ArgumentParser/Usage/UsageGenerator.swift
@@ -9,7 +9,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 internal import protocol Foundation.LocalizedError
 #else
 import protocol Foundation.LocalizedError
diff --git a/Sources/ArgumentParser/Utilities/Mutex.swift b/Sources/ArgumentParser/Utilities/Mutex.swift
index 2f3bd040d..3a3c4244b 100644
--- a/Sources/ArgumentParser/Utilities/Mutex.swift
+++ b/Sources/ArgumentParser/Utilities/Mutex.swift
@@ -9,7 +9,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 internal import Foundation
 #else
 import Foundation
diff --git a/Sources/ArgumentParserTestHelpers/StringHelpers.swift b/Sources/ArgumentParserTestHelpers/StringHelpers.swift
index 5baf377b0..639ed4479 100644
--- a/Sources/ArgumentParserTestHelpers/StringHelpers.swift
+++ b/Sources/ArgumentParserTestHelpers/StringHelpers.swift
@@ -9,6 +9,12 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if compiler(>=6.0)
+internal import Foundation
+#else
+import Foundation
+#endif
+
 extension Substring {
   func trimmed() -> Substring {
     guard let i = lastIndex(where: { $0 != " " }) else {
diff --git a/Tests/ArgumentParserExampleTests/MathExampleTests.swift b/Tests/ArgumentParserExampleTests/MathExampleTests.swift
index f1928f915..2c9a666cb 100644
--- a/Tests/ArgumentParserExampleTests/MathExampleTests.swift
+++ b/Tests/ArgumentParserExampleTests/MathExampleTests.swift
@@ -9,15 +9,10 @@
 //
 //===----------------------------------------------------------------------===//
 
-import ArgumentParser
 import ArgumentParserTestHelpers
 import XCTest
 
-#if swift(>=6.0)
-@testable internal import struct ArgumentParser.CompletionShell
-#else
-@testable import struct ArgumentParser.CompletionShell
-#endif
+@testable import ArgumentParser
 
 final class MathExampleTests: XCTestCase {
   override func setUp() {
diff --git a/Tests/ArgumentParserExampleTests/RepeatExampleTests.swift b/Tests/ArgumentParserExampleTests/RepeatExampleTests.swift
index b0ff5ece8..4410289eb 100644
--- a/Tests/ArgumentParserExampleTests/RepeatExampleTests.swift
+++ b/Tests/ArgumentParserExampleTests/RepeatExampleTests.swift
@@ -9,6 +9,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+import ArgumentParser
 import ArgumentParserTestHelpers
 import XCTest
 
diff --git a/Tests/ArgumentParserExampleTests/RollDiceExampleTests.swift b/Tests/ArgumentParserExampleTests/RollDiceExampleTests.swift
index 2d508f2bc..e8abeaf21 100644
--- a/Tests/ArgumentParserExampleTests/RollDiceExampleTests.swift
+++ b/Tests/ArgumentParserExampleTests/RollDiceExampleTests.swift
@@ -9,6 +9,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+import ArgumentParser
 import ArgumentParserTestHelpers
 import XCTest