diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 5f22654..1ddfbe3 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -7,19 +7,6 @@ on:
     branches: [ master ]
 
 jobs:
-  test-package-plugin-macos-12:
-    name: Test Package Plugin
-    runs-on: macos-12
-    strategy:
-      fail-fast: false
-      matrix:
-        xcode:
-        - '13.4.1' # Swift 5.6
-    steps:
-      - uses: actions/checkout@v2
-      - name: Test Package Plugin
-        run: swift package --allow-writing-to-package-directory format --lint
-
   test-package-plugin-macos-13:
     name: Test Package Plugin
     runs-on: macos-13
diff --git a/Package.swift b/Package.swift
index 91b9c89..b5e5dff 100644
--- a/Package.swift
+++ b/Package.swift
@@ -1,9 +1,9 @@
-// swift-tools-version: 5.6
+// swift-tools-version: 5.8
 import PackageDescription
 
 let package = Package(
     name: "RakuyoSwift",
-    platforms: [.macOS(.v10_13)],
+    platforms: [.macOS(.v13)],
     products: [
         .plugin(name: "FormatSwift", targets: ["FormatSwift"]),
     ],
diff --git a/Sources/RakuyoSwiftFormatTool/RakuyoSwiftFormatTool.swift b/Sources/RakuyoSwiftFormatTool/RakuyoSwiftFormatTool.swift
index f901e52..2bea39f 100644
--- a/Sources/RakuyoSwiftFormatTool/RakuyoSwiftFormatTool.swift
+++ b/Sources/RakuyoSwiftFormatTool/RakuyoSwiftFormatTool.swift
@@ -84,7 +84,7 @@ extension RakuyoSwiftFormatTool {
         }
         
         if
-            let swiftLintAutocorrectExitCode = swiftLintAutocorrectExitCode,
+            let swiftLintAutocorrectExitCode,
             swiftLintAutocorrectExitCode != EXIT_SUCCESS
         {
             throw ExitCode(swiftLintAutocorrectExitCode)
@@ -104,7 +104,7 @@ extension RakuyoSwiftFormatTool {
             "--config", swiftFormatConfig,
         ]
         
-        if let swiftFormatCachePath = swiftFormatCachePath {
+        if let swiftFormatCachePath {
             arguments += ["--cache", swiftFormatCachePath]
         }
         
@@ -112,7 +112,7 @@ extension RakuyoSwiftFormatTool {
             arguments += ["--lint"]
         }
         
-        if let swiftVersion = swiftVersion {
+        if let swiftVersion {
             arguments += ["--swiftversion", swiftVersion]
         }
         
@@ -133,7 +133,7 @@ extension RakuyoSwiftFormatTool {
             "--strict",
         ]
         
-        if let swiftLintCachePath = swiftLintCachePath {
+        if let swiftLintCachePath {
             arguments += ["--cache-path", swiftLintCachePath]
         }