diff --git a/.swift-version b/.swift-version
index a3ec5a4..5186d07 100644
--- a/.swift-version
+++ b/.swift-version
@@ -1 +1 @@
-3.2
+4.0
diff --git a/Cartfile b/Cartfile
index 04bd4ee..6240513 100644
--- a/Cartfile
+++ b/Cartfile
@@ -1,2 +1,2 @@
-github "antitypical/Result" >= 3.0
-github "ReactiveX/RxSwift" ~> 3.0
+github "antitypical/Result" ~> 3.0
+github "ReactiveX/RxSwift" ~> 4.0
diff --git a/Cartfile.resolved b/Cartfile.resolved
index 2abb65c..573512a 100644
--- a/Cartfile.resolved
+++ b/Cartfile.resolved
@@ -1,2 +1,2 @@
-github "ReactiveX/RxSwift" "3.6.1"
+github "ReactiveX/RxSwift" "4.0.0"
 github "antitypical/Result" "3.2.4"
diff --git a/Example/Podfile b/Example/Podfile
index b94e622..f897fe0 100644
--- a/Example/Podfile
+++ b/Example/Podfile
@@ -7,13 +7,13 @@ inhibit_all_warnings!
 
 target 'ReCaptcha_Example' do
   pod 'ReCaptcha/RxSwift', :path => '../'
-  pod 'RxCocoa', '~> 3.0'
+  pod 'RxCocoa', '~> 4.0'
   pod 'SwiftLint', '~> 0.23'
 
   target 'ReCaptcha_Tests' do
     inherit! :search_paths
 
-    pod 'AppSwizzle', '~> 1.1'
+    pod 'AppSwizzle', :git => 'git@github.com:fjcaetano/AppSwizzle.git', :branch => 'swift4'
   end
 end
 
diff --git a/Example/Podfile.lock b/Example/Podfile.lock
index f9b113d..a725868 100644
--- a/Example/Podfile.lock
+++ b/Example/Podfile.lock
@@ -1,34 +1,42 @@
 PODS:
-  - AppSwizzle (1.1.2)
+  - AppSwizzle (1.2)
   - ReCaptcha/Core (0.3.0):
     - Result (~> 3.0)
   - ReCaptcha/RxSwift (0.3.0):
     - ReCaptcha/Core
-    - RxSwift (~> 3.0)
+    - RxSwift (~> 4.0)
   - Result (3.2.4)
-  - RxCocoa (3.6.1):
-    - RxSwift (~> 3.6)
-  - RxSwift (3.6.1)
+  - RxCocoa (4.0.0):
+    - RxSwift (~> 4.0)
+  - RxSwift (4.0.0)
   - SwiftLint (0.23.1)
 
 DEPENDENCIES:
-  - AppSwizzle (~> 1.1)
+  - AppSwizzle (from `git@github.com:fjcaetano/AppSwizzle.git`, branch `swift4`)
   - ReCaptcha/RxSwift (from `../`)
-  - RxCocoa (~> 3.0)
+  - RxCocoa (~> 4.0)
   - SwiftLint (~> 0.23)
 
 EXTERNAL SOURCES:
+  AppSwizzle:
+    :branch: swift4
+    :git: git@github.com:fjcaetano/AppSwizzle.git
   ReCaptcha:
     :path: ../
 
+CHECKOUT OPTIONS:
+  AppSwizzle:
+    :commit: c432a73e43779d20ef8e8a589aabd9622b7b6a5d
+    :git: git@github.com:fjcaetano/AppSwizzle.git
+
 SPEC CHECKSUMS:
-  AppSwizzle: 45d1a9d71821e7e1bb3a2a503c2979ca6fe4e46d
-  ReCaptcha: 0ecf1105cae5040557d8b470909dda5196853c15
+  AppSwizzle: bbd3782652fc426ce59c045a92ec61d36f261984
+  ReCaptcha: a08f541158ddf69ece271ee476a7843fd484aa2c
   Result: d2d07204ce72856f1fd9130bbe42c35a7b0fea10
-  RxCocoa: 84a08739ab186248c7f31ce4ee92d6f8a947d690
-  RxSwift: f9de85ea20cd2f7716ee5409fc13523dc638e4e4
+  RxCocoa: d62846ca96495d862fa4c59ea7d87e5031d7340e
+  RxSwift: fd680d75283beb5e2559486f3c0ff852f0d35334
   SwiftLint: 1b670ce79284c76520f84060e87d645078fd32fa
 
-PODFILE CHECKSUM: 297c41fe46ada741f20f242a63e577d52fa47001
+PODFILE CHECKSUM: b22c55655f09e6f7d188835d6914c58236e5956e
 
 COCOAPODS: 1.3.1
diff --git a/Example/ReCaptcha.xcodeproj/project.pbxproj b/Example/ReCaptcha.xcodeproj/project.pbxproj
index 656a6a9..707d3c4 100644
--- a/Example/ReCaptcha.xcodeproj/project.pbxproj
+++ b/Example/ReCaptcha.xcodeproj/project.pbxproj
@@ -258,11 +258,12 @@
 				TargetAttributes = {
 					607FACCF1AFB9204008FA782 = {
 						CreatedOnToolsVersion = 6.3.1;
-						LastSwiftMigration = 0820;
+						LastSwiftMigration = 0900;
 					};
 					F2ECCF751E9FC47B0097B199 = {
 						CreatedOnToolsVersion = 8.3;
 						DevelopmentTeam = 58EEZG76L8;
+						LastSwiftMigration = 0900;
 						ProvisioningStyle = Automatic;
 						TestTargetID = 607FACCF1AFB9204008FA782;
 					};
@@ -598,7 +599,8 @@
 				MODULE_NAME = ExampleApp;
 				PRODUCT_BUNDLE_IDENTIFIER = "com.flaviocaetano.ReCaptcha-Example";
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_VERSION = 3.0;
+				SWIFT_SWIFT3_OBJC_INFERENCE = Default;
+				SWIFT_VERSION = 4.0;
 			};
 			name = Debug;
 		};
@@ -613,7 +615,8 @@
 				MODULE_NAME = ExampleApp;
 				PRODUCT_BUNDLE_IDENTIFIER = "com.flaviocaetano.ReCaptcha-Example";
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_VERSION = 3.0;
+				SWIFT_SWIFT3_OBJC_INFERENCE = Default;
+				SWIFT_VERSION = 4.0;
 			};
 			name = Release;
 		};
@@ -633,7 +636,8 @@
 				PRODUCT_BUNDLE_IDENTIFIER = "com.flaviocaetano.ReCaptcha-Tests";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SWIFT_ACTIVE_COMPILATION_CONDITIONS = DEBUG;
-				SWIFT_VERSION = 3.0;
+				SWIFT_SWIFT3_OBJC_INFERENCE = Default;
+				SWIFT_VERSION = 4.0;
 				TEST_HOST = "$(BUILT_PRODUCTS_DIR)/ReCaptcha_Example.app/ReCaptcha_Example";
 			};
 			name = Debug;
@@ -652,7 +656,8 @@
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = "com.flaviocaetano.ReCaptcha-Tests";
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_VERSION = 3.0;
+				SWIFT_SWIFT3_OBJC_INFERENCE = Default;
+				SWIFT_VERSION = 4.0;
 				TEST_HOST = "$(BUILT_PRODUCTS_DIR)/ReCaptcha_Example.app/ReCaptcha_Example";
 			};
 			name = Release;
diff --git a/ReCaptcha.podspec b/ReCaptcha.podspec
index 4d06517..bc873af 100644
--- a/ReCaptcha.podspec
+++ b/ReCaptcha.podspec
@@ -32,6 +32,6 @@ invisibility is not possible.
   s.subspec 'RxSwift' do |rx|
     rx.source_files = 'ReCaptcha/Classes/Rx/**/*'
     rx.dependency 'ReCaptcha/Core'
-    rx.dependency 'RxSwift', '~> 3.0'
+    rx.dependency 'RxSwift', '~> 4.0'
   end
 end
diff --git a/fastlane/Fastfile b/fastlane/Fastfile
index 23c2a94..dcf566a 100644
--- a/fastlane/Fastfile
+++ b/fastlane/Fastfile
@@ -55,7 +55,7 @@ platform :ios do
   desc "Lint Carthage lib"
   lane :carthage_lint do
     carthage(
-      command: "bootstrap",
+      command: "update",
       platform: "iOS",
       cache_builds: true,
     )