diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 400a1b9..3f449b2 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -11,8 +11,8 @@ jobs:
     name: Unit tests
     uses: apple/swift-nio/.github/workflows/unit_tests.yml@main
     with:
-      linux_5_9_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
-      linux_5_10_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
+      linux_5_9_arguments_override: "--explicit-target-dependency-import-check error"
+      linux_5_10_arguments_override: "--explicit-target-dependency-import-check error"
       linux_6_0_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"
       linux_nightly_6_0_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"
       linux_nightly_main_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"
diff --git a/.github/workflows/pull_request.yml b/.github/workflows/pull_request.yml
index 6287586..1e21cc2 100644
--- a/.github/workflows/pull_request.yml
+++ b/.github/workflows/pull_request.yml
@@ -15,8 +15,8 @@ jobs:
     name: Unit tests
     uses: apple/swift-nio/.github/workflows/unit_tests.yml@main
     with:
-      linux_5_9_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
-      linux_5_10_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
+      linux_5_9_arguments_override: "--explicit-target-dependency-import-check error"
+      linux_5_10_arguments_override: "--explicit-target-dependency-import-check error"
       linux_6_0_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"
       linux_nightly_6_0_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"
       linux_nightly_main_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"
diff --git a/Package.swift b/Package.swift
index a4ace72..8520635 100644
--- a/Package.swift
+++ b/Package.swift
@@ -1,4 +1,4 @@
-// swift-tools-version:5.8
+// swift-tools-version:5.9
 //===----------------------------------------------------------------------===//
 //
 // This source file is part of the Swift Metrics API open source project
@@ -40,3 +40,9 @@ let package = Package(
         ),
     ]
 )
+
+for target in package.targets {
+    var settings = target.swiftSettings ?? []
+    settings.append(.enableExperimentalFeature("StrictConcurrency=complete"))
+    target.swiftSettings = settings
+}