diff --git a/.travis.yml b/.travis.yml
index e7e7d5e..94f26d6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,7 +5,7 @@ language: generic
 sudo: required
 dist: trusty
 
-osx_image: xcode8.3
+osx_image: xcode9
 before_install:
     - if [ $TRAVIS_OS_NAME == "osx" ]; then
             brew tap vapor/tap;
@@ -23,7 +23,7 @@ script:
     - swift test
 
 after_success:
-    - eval "$(curl -sL https://raw.githubusercontent.com/vapor-community/swift/master/codecov)"
+    - eval "$(curl -sL https://raw.githubusercontent.com/vapor-community/swift/swift-4-codecov/codecov-swift4)"
 
 notifications:
   email:
diff --git a/Package@swift-4.swift b/Package@swift-4.swift
new file mode 100644
index 0000000..6b55ca5
--- /dev/null
+++ b/Package@swift-4.swift
@@ -0,0 +1,18 @@
+// swift-tools-version:4.0
+
+import PackageDescription
+
+let package = Package(
+    name: "VaporOAuth",
+    products: [
+        .library(name: "VaporOAuth", targets: ["VaporOAuth"]),
+    ],
+    dependencies: [
+    	.package(url: "https://github.com/vapor/vapor.git", .upToNextMajor(from: "2.2.0")),
+        .package(url: "https://github.com/vapor/auth-provider.git", .upToNextMajor(from: "1.2.0")),
+    ],
+    targets: [
+        .target(name: "VaporOAuth", dependencies: ["Vapor", "AuthProvider"]),
+        .testTarget(name: "VaporOAuthTests", dependencies: ["VaporOAuth"]),
+    ]
+)
diff --git a/README.md b/README.md
index 9d814ca..2fcafea 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,7 @@
     <br>
     <br>
     <a href="https://swift.org">
-        <img src="http://img.shields.io/badge/Swift-3.1-brightgreen.svg" alt="Language">
+        <img src="http://img.shields.io/badge/Swift-4-brightgreen.svg" alt="Language">
     </a>
     <a href="https://travis-ci.org/brokenhandsio/vapor-oauth">
         <img src="https://travis-ci.org/brokenhandsio/vapor-oauth.svg?branch=master" alt="Build Status">
@@ -40,7 +40,7 @@ Vapor OAuth can be added to your Vapor add with a simple provider. To get starte
 ```swift
 dependencies: [
     ...,
-    .Package(url: "https://github.com/brokenhandsio/vapor-oauth", majorVersion: 0)
+    .package(url: "https://github.com/brokenhandsio/vapor-oauth", from: "0.6.0"))
 ]
 ```
 
diff --git a/Sources/VaporOAuth/Helper/Helper.swift b/Sources/VaporOAuth/Helper/Helper.swift
index d216659..7ac47e9 100644
--- a/Sources/VaporOAuth/Helper/Helper.swift
+++ b/Sources/VaporOAuth/Helper/Helper.swift
@@ -60,7 +60,11 @@ extension Request {
             throw Abort(.forbidden)
         }
 
+        #if swift(>=4)
+        let token  = String(authHeader[authHeader.index(authHeader.startIndex, offsetBy: 7)...])
+        #else
         let token = authHeader.substring(from: authHeader.index(authHeader.startIndex, offsetBy: 7))
+        #endif
 
         guard !token.isEmpty else {
             throw Abort(.forbidden)
diff --git a/Tests/VaporOAuthTests/AuthorizationTests/AuthorizationRequestTests.swift b/Tests/VaporOAuthTests/AuthorizationTests/AuthorizationRequestTests.swift
index 271ff59..87c5916 100644
--- a/Tests/VaporOAuthTests/AuthorizationTests/AuthorizationRequestTests.swift
+++ b/Tests/VaporOAuthTests/AuthorizationTests/AuthorizationRequestTests.swift
@@ -57,7 +57,7 @@ class AuthorizationRequestTests: XCTestCase {
         #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
             let thisClass = type(of: self)
             let linuxCount = thisClass.allTests.count
-            let darwinCount = Int(thisClass.defaultTestSuite().testCaseCount)
+            let darwinCount = Int(thisClass.defaultTestSuite.testCaseCount)
             XCTAssertEqual(linuxCount, darwinCount, "\(darwinCount - linuxCount) tests are missing from allTests")
         #endif
     }
diff --git a/Tests/VaporOAuthTests/AuthorizationTests/AuthorizationResponseTests.swift b/Tests/VaporOAuthTests/AuthorizationTests/AuthorizationResponseTests.swift
index 3b4ee40..ee39a4f 100644
--- a/Tests/VaporOAuthTests/AuthorizationTests/AuthorizationResponseTests.swift
+++ b/Tests/VaporOAuthTests/AuthorizationTests/AuthorizationResponseTests.swift
@@ -72,7 +72,7 @@ class AuthorizationResponseTests: XCTestCase {
         #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
             let thisClass = type(of: self)
             let linuxCount = thisClass.allTests.count
-            let darwinCount = Int(thisClass.defaultTestSuite().testCaseCount)
+            let darwinCount = Int(thisClass.defaultTestSuite.testCaseCount)
             XCTAssertEqual(linuxCount, darwinCount, "\(darwinCount - linuxCount) tests are missing from allTests")
         #endif
     }
diff --git a/Tests/VaporOAuthTests/DefaultImplementationTests/DefaultImplementationTests.swift b/Tests/VaporOAuthTests/DefaultImplementationTests/DefaultImplementationTests.swift
index 941554d..e10d20a 100644
--- a/Tests/VaporOAuthTests/DefaultImplementationTests/DefaultImplementationTests.swift
+++ b/Tests/VaporOAuthTests/DefaultImplementationTests/DefaultImplementationTests.swift
@@ -34,7 +34,7 @@ class DefaultImplementationTests: XCTestCase {
         #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
             let thisClass = type(of: self)
             let linuxCount = thisClass.allTests.count
-            let darwinCount = Int(thisClass.defaultTestSuite().testCaseCount)
+            let darwinCount = Int(thisClass.defaultTestSuite.testCaseCount)
             XCTAssertEqual(linuxCount, darwinCount, "\(darwinCount - linuxCount) tests are missing from allTests")
         #endif
     }
diff --git a/Tests/VaporOAuthTests/GrantTests/AuthorizationCodeTokenTests.swift b/Tests/VaporOAuthTests/GrantTests/AuthorizationCodeTokenTests.swift
index 48632f7..88624ed 100644
--- a/Tests/VaporOAuthTests/GrantTests/AuthorizationCodeTokenTests.swift
+++ b/Tests/VaporOAuthTests/GrantTests/AuthorizationCodeTokenTests.swift
@@ -66,7 +66,7 @@ class AuthorizationCodeTokenTests: XCTestCase {
         #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
             let thisClass = type(of: self)
             let linuxCount = thisClass.allTests.count
-            let darwinCount = Int(thisClass.defaultTestSuite().testCaseCount)
+            let darwinCount = Int(thisClass.defaultTestSuite.testCaseCount)
             XCTAssertEqual(linuxCount, darwinCount, "\(darwinCount - linuxCount) tests are missing from allTests")
         #endif
     }
diff --git a/Tests/VaporOAuthTests/GrantTests/ClientCredentialsTokenTests.swift b/Tests/VaporOAuthTests/GrantTests/ClientCredentialsTokenTests.swift
index 5a94fef..ef0bcff 100644
--- a/Tests/VaporOAuthTests/GrantTests/ClientCredentialsTokenTests.swift
+++ b/Tests/VaporOAuthTests/GrantTests/ClientCredentialsTokenTests.swift
@@ -61,7 +61,7 @@ class ClientCredentialsTokenTests: XCTestCase {
         #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
             let thisClass = type(of: self)
             let linuxCount = thisClass.allTests.count
-            let darwinCount = Int(thisClass.defaultTestSuite().testCaseCount)
+            let darwinCount = Int(thisClass.defaultTestSuite.testCaseCount)
             XCTAssertEqual(linuxCount, darwinCount, "\(darwinCount - linuxCount) tests are missing from allTests")
         #endif
     }
diff --git a/Tests/VaporOAuthTests/GrantTests/ImplicitGrantTests.swift b/Tests/VaporOAuthTests/GrantTests/ImplicitGrantTests.swift
index 3b14881..a9faad4 100644
--- a/Tests/VaporOAuthTests/GrantTests/ImplicitGrantTests.swift
+++ b/Tests/VaporOAuthTests/GrantTests/ImplicitGrantTests.swift
@@ -88,7 +88,7 @@ class ImplicitGrantTests: XCTestCase {
         #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
             let thisClass = type(of: self)
             let linuxCount = thisClass.allTests.count
-            let darwinCount = Int(thisClass.defaultTestSuite().testCaseCount)
+            let darwinCount = Int(thisClass.defaultTestSuite.testCaseCount)
             XCTAssertEqual(linuxCount, darwinCount, "\(darwinCount - linuxCount) tests are missing from allTests")
         #endif
     }
diff --git a/Tests/VaporOAuthTests/GrantTests/PasswordGrantTokenTests.swift b/Tests/VaporOAuthTests/GrantTests/PasswordGrantTokenTests.swift
index 6ca15fc..a4ea1dd 100644
--- a/Tests/VaporOAuthTests/GrantTests/PasswordGrantTokenTests.swift
+++ b/Tests/VaporOAuthTests/GrantTests/PasswordGrantTokenTests.swift
@@ -73,7 +73,7 @@ class PasswordGrantTokenTests: XCTestCase {
         #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
             let thisClass = type(of: self)
             let linuxCount = thisClass.allTests.count
-            let darwinCount = Int(thisClass.defaultTestSuite().testCaseCount)
+            let darwinCount = Int(thisClass.defaultTestSuite.testCaseCount)
             XCTAssertEqual(linuxCount, darwinCount, "\(darwinCount - linuxCount) tests are missing from allTests")
         #endif
     }
diff --git a/Tests/VaporOAuthTests/GrantTests/TokenRefreshTests.swift b/Tests/VaporOAuthTests/GrantTests/TokenRefreshTests.swift
index 300d6e4..8e46103 100644
--- a/Tests/VaporOAuthTests/GrantTests/TokenRefreshTests.swift
+++ b/Tests/VaporOAuthTests/GrantTests/TokenRefreshTests.swift
@@ -64,7 +64,7 @@ class TokenRefreshTests: XCTestCase {
         #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
             let thisClass = type(of: self)
             let linuxCount = thisClass.allTests.count
-            let darwinCount = Int(thisClass.defaultTestSuite().testCaseCount)
+            let darwinCount = Int(thisClass.defaultTestSuite.testCaseCount)
             XCTAssertEqual(linuxCount, darwinCount, "\(darwinCount - linuxCount) tests are missing from allTests")
         #endif
     }
diff --git a/Tests/VaporOAuthTests/IntegrationTests/AuthCodeResourceServerTests.swift b/Tests/VaporOAuthTests/IntegrationTests/AuthCodeResourceServerTests.swift
index e4d19f3..66fa448 100644
--- a/Tests/VaporOAuthTests/IntegrationTests/AuthCodeResourceServerTests.swift
+++ b/Tests/VaporOAuthTests/IntegrationTests/AuthCodeResourceServerTests.swift
@@ -68,7 +68,7 @@ class AuthCodeResourceServerTests: XCTestCase {
         #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
             let thisClass = type(of: self)
             let linuxCount = thisClass.allTests.count
-            let darwinCount = Int(thisClass.defaultTestSuite().testCaseCount)
+            let darwinCount = Int(thisClass.defaultTestSuite.testCaseCount)
             XCTAssertEqual(linuxCount, darwinCount, "\(darwinCount - linuxCount) tests are missing from allTests")
         #endif
     }
@@ -117,7 +117,7 @@ class AuthCodeResourceServerTests: XCTestCase {
         for queryPart in queryParts {
             if queryPart.hasPrefix("code=") {
                 let codeStartIndex = queryPart.index(queryPart.startIndex, offsetBy: 5)
-                codePart = queryPart.substring(from: codeStartIndex)
+                codePart = String(queryPart[codeStartIndex...])
             }
         }
         
diff --git a/Tests/VaporOAuthTests/TokenIntrospectionTests/TokenIntrospectionTests.swift b/Tests/VaporOAuthTests/TokenIntrospectionTests/TokenIntrospectionTests.swift
index d92c175..75e5e55 100644
--- a/Tests/VaporOAuthTests/TokenIntrospectionTests/TokenIntrospectionTests.swift
+++ b/Tests/VaporOAuthTests/TokenIntrospectionTests/TokenIntrospectionTests.swift
@@ -57,7 +57,7 @@ class TokenIntrospectionTests: XCTestCase {
         #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
             let thisClass = type(of: self)
             let linuxCount = thisClass.allTests.count
-            let darwinCount = Int(thisClass.defaultTestSuite().testCaseCount)
+            let darwinCount = Int(thisClass.defaultTestSuite.testCaseCount)
             XCTAssertEqual(linuxCount, darwinCount, "\(darwinCount - linuxCount) tests are missing from allTests")
         #endif
     }