diff --git a/.github/workflows/swift.yml b/.github/workflows/swift.yml
index 400ff99..d2a84ba 100644
--- a/.github/workflows/swift.yml
+++ b/.github/workflows/swift.yml
@@ -15,7 +15,7 @@ jobs:
         os: [macos-latest, ubuntu-latest]
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - run: swift build -v
   
   test:
@@ -26,5 +26,5 @@ jobs:
         os: [macos-latest, ubuntu-latest]
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - run: swift test -v
diff --git a/.github/workflows/swiftlint.yml b/.github/workflows/swiftlint.yml
index 986cf15..93c3f9f 100644
--- a/.github/workflows/swiftlint.yml
+++ b/.github/workflows/swiftlint.yml
@@ -22,7 +22,7 @@ jobs:
     name: SwiftLint
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - uses: norio-nomura/action-swiftlint@3.2.1
         with:
           args: --strict
diff --git a/Sources/MultipartFormData/Boundary.swift b/Sources/MultipartFormData/Boundary.swift
index c75db98..251178f 100644
--- a/Sources/MultipartFormData/Boundary.swift
+++ b/Sources/MultipartFormData/Boundary.swift
@@ -104,6 +104,6 @@ extension Boundary: CustomDebugStringConvertible {
 
 extension Boundary {
     internal var _value: String {
-        return String(decoding: _asciiData, as: UTF8.self) // UTF-8 representation is exactly equivalent to ASCII
+        return String(bytes: _asciiData, encoding: .ascii) ?? ""
     }
 }
diff --git a/Sources/MultipartFormData/Internal/String+helpers.swift b/Sources/MultipartFormData/Internal/String+helpers.swift
index e349138..e7283d2 100644
--- a/Sources/MultipartFormData/Internal/String+helpers.swift
+++ b/Sources/MultipartFormData/Internal/String+helpers.swift
@@ -7,6 +7,7 @@
 
 extension String {
     internal init(_ staticString: StaticString) {
+        // swiftlint:disable:next optional_data_string_conversion
         self = staticString.withUTF8Buffer { String(decoding: $0, as: UTF8.self) }
     }
 }
diff --git a/Sources/MultipartFormData/MultipartFormData.swift b/Sources/MultipartFormData/MultipartFormData.swift
index a29ac59..f8dac25 100644
--- a/Sources/MultipartFormData/MultipartFormData.swift
+++ b/Sources/MultipartFormData/MultipartFormData.swift
@@ -162,6 +162,7 @@ extension MultipartFormData {
 
 extension MultipartFormData: CustomDebugStringConvertible {
     public var debugDescription: String {
-        return String(decoding: contentType._data + ._crlf + ._crlf + httpBody, as: UTF8.self)
+        let bytes: Data = contentType._data + ._crlf + ._crlf + httpBody
+        return String(bytes: bytes, encoding: .utf8) ?? ""
     }
 }
diff --git a/Sources/MultipartFormData/Subpart.swift b/Sources/MultipartFormData/Subpart.swift
index 37ef512..c88e7c7 100644
--- a/Sources/MultipartFormData/Subpart.swift
+++ b/Sources/MultipartFormData/Subpart.swift
@@ -80,7 +80,7 @@ extension Subpart {
 
 extension Subpart: CustomDebugStringConvertible {
     public var debugDescription: String {
-        return String(decoding: _data, as: UTF8.self)
+        return String(bytes: _data, encoding: .utf8) ?? ""
     }
 }
 
diff --git a/Tests/MultipartFormDataTests/ContentDispositionTests.swift b/Tests/MultipartFormDataTests/ContentDispositionTests.swift
index 71ce853..227fd89 100644
--- a/Tests/MultipartFormDataTests/ContentDispositionTests.swift
+++ b/Tests/MultipartFormDataTests/ContentDispositionTests.swift
@@ -9,28 +9,36 @@ import XCTest
 @testable import MultipartFormData
 
 final class ContentDispositionTests: XCTestCase {
-    func testPercentEncodingError() throws {
+    func testUncheckedInitValid() {
         XCTAssertNoThrow(try ContentDisposition(uncheckedName: "a", uncheckedFilename: "a"))
-        
+    }
+    
+    func testUncheckedInitInvalid() throws {
         // https://stackoverflow.com/questions/33558933/why-is-the-return-value-of-string-addingpercentencoding-optional
-        // does not work on Linux, can still encoding there
-        let nonPercentEncodableString = try XCTUnwrap(String(bytes: [0xD8, 0x00] as [UInt8], encoding: .utf16BigEndian))
-        if nonPercentEncodableString.addingPercentEncoding(withAllowedCharacters: .urlPathAllowed) == nil {
-            XCTAssertThrowsError(try ContentDisposition(uncheckedName: nonPercentEncodableString, uncheckedFilename: nil))
-            XCTAssertThrowsError(try ContentDisposition(uncheckedName: "", uncheckedFilename: nonPercentEncodableString))
+        let bytes: [UInt8] = [0xD8, 0x00]
+        
+        // Ensure the non-encodable string can be created, e.g. on iOS 18 it no longer works.
+        guard let nonPercentEncodableString = String(bytes: bytes, encoding: .utf16BigEndian) else {
+            throw XCTSkip("UTF16 byte encoding failed")
         }
+        
+        // Ensure the percent-encoding fails on the current platform, e.g. on Linux it encodes.
+        guard nonPercentEncodableString.addingPercentEncoding(withAllowedCharacters: .urlPathAllowed) == nil else {
+            throw XCTSkip("percent encoding didn't fail")
+        }
+        
+        XCTAssertThrowsError(try ContentDisposition(uncheckedName: nonPercentEncodableString, uncheckedFilename: nil))
+        XCTAssertThrowsError(try ContentDisposition(uncheckedName: "", uncheckedFilename: nonPercentEncodableString))
     }
     
     func testParameters() throws {
         let contentDisposition = ContentDisposition(name: "a", filename: "a")
-        
         XCTAssertEqual(contentDisposition.parameters[0], HTTPHeaderParameter("name", value: "a"))
         XCTAssertEqual(contentDisposition.parameters[1], HTTPHeaderParameter("filename", value: "a"))
     }
     
     func testData() throws {
         let contentDisposition = ContentDisposition(name: "a", filename: "a")
-        
         XCTAssertEqual(contentDisposition._data, Data("Content-Disposition: form-data; name=\"a\"; filename=\"a\"".utf8))
     }
 }