diff --git a/.swift-version b/.swift-version
index 06a4457..389f774 100644
--- a/.swift-version
+++ b/.swift-version
@@ -1 +1 @@
-3.1
\ No newline at end of file
+4.0
\ No newline at end of file
diff --git a/MapleBacon.podspec b/MapleBacon.podspec
index 7308773..15a832d 100644
--- a/MapleBacon.podspec
+++ b/MapleBacon.podspec
@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name         = "MapleBacon"
-  s.version      = "3.1.0"
+  s.version      = "4.0.0"
   s.summary      = "A delicious image download and caching library for iOS"
   s.description  = <<-DESC
                   A delicious image download and caching library for iOS. Background downloads, caching and scaling.
diff --git a/MapleBacon.xcodeproj/project.pbxproj b/MapleBacon.xcodeproj/project.pbxproj
index 7d207b5..b996d0e 100644
--- a/MapleBacon.xcodeproj/project.pbxproj
+++ b/MapleBacon.xcodeproj/project.pbxproj
@@ -297,7 +297,7 @@
 			attributes = {
 				LastSwiftMigration = 0700;
 				LastSwiftUpdateCheck = 0700;
-				LastUpgradeCheck = 0800;
+				LastUpgradeCheck = 0900;
 				ORGANIZATIONNAME = "Zalando SE";
 				TargetAttributes = {
 					946B985A1C0C432B00B0276E = {
@@ -305,11 +305,11 @@
 					};
 					F2520C471A3EDAFE0061BB33 = {
 						CreatedOnToolsVersion = 6.1.1;
-						LastSwiftMigration = 0800;
+						LastSwiftMigration = 0900;
 					};
 					F2520C521A3EDAFF0061BB33 = {
 						CreatedOnToolsVersion = 6.1.1;
-						LastSwiftMigration = 0800;
+						LastSwiftMigration = 0900;
 					};
 				};
 			};
@@ -430,6 +430,7 @@
 				PRODUCT_NAME = MapleBacon;
 				SDKROOT = appletvos;
 				SKIP_INSTALL = YES;
+				SWIFT_VERSION = 4.0;
 				TARGETED_DEVICE_FAMILY = 3;
 				TVOS_DEPLOYMENT_TARGET = 9.0;
 			};
@@ -454,6 +455,7 @@
 				PRODUCT_NAME = MapleBacon;
 				SDKROOT = appletvos;
 				SKIP_INSTALL = YES;
+				SWIFT_VERSION = 4.0;
 				TARGETED_DEVICE_FAMILY = 3;
 				TVOS_DEPLOYMENT_TARGET = 9.0;
 			};
@@ -467,14 +469,20 @@
 				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_MODULES = YES;
 				CLANG_ENABLE_OBJC_ARC = YES;
+				CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;
 				CLANG_WARN_BOOL_CONVERSION = YES;
+				CLANG_WARN_COMMA = YES;
 				CLANG_WARN_CONSTANT_CONVERSION = YES;
 				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
 				CLANG_WARN_EMPTY_BODY = YES;
 				CLANG_WARN_ENUM_CONVERSION = YES;
 				CLANG_WARN_INFINITE_RECURSION = YES;
 				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
 				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
+				CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
+				CLANG_WARN_STRICT_PROTOTYPES = YES;
 				CLANG_WARN_SUSPICIOUS_MOVE = YES;
 				CLANG_WARN_UNREACHABLE_CODE = YES;
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
@@ -517,14 +525,20 @@
 				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_MODULES = YES;
 				CLANG_ENABLE_OBJC_ARC = YES;
+				CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;
 				CLANG_WARN_BOOL_CONVERSION = YES;
+				CLANG_WARN_COMMA = YES;
 				CLANG_WARN_CONSTANT_CONVERSION = YES;
 				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
 				CLANG_WARN_EMPTY_BODY = YES;
 				CLANG_WARN_ENUM_CONVERSION = YES;
 				CLANG_WARN_INFINITE_RECURSION = YES;
 				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
 				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
+				CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
+				CLANG_WARN_STRICT_PROTOTYPES = YES;
 				CLANG_WARN_SUSPICIOUS_MOVE = YES;
 				CLANG_WARN_UNREACHABLE_CODE = YES;
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
@@ -572,7 +586,8 @@
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SKIP_INSTALL = YES;
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
-				SWIFT_VERSION = 3.0;
+				SWIFT_SWIFT3_OBJC_INFERENCE = Default;
+				SWIFT_VERSION = 4.0;
 			};
 			name = Debug;
 		};
@@ -595,7 +610,8 @@
 				PRODUCT_BUNDLE_IDENTIFIER = com.zalando.MapleBacon;
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SKIP_INSTALL = YES;
-				SWIFT_VERSION = 3.0;
+				SWIFT_SWIFT3_OBJC_INFERENCE = Default;
+				SWIFT_VERSION = 4.0;
 			};
 			name = Release;
 		};
@@ -613,7 +629,8 @@
 				INFOPLIST_FILE = "$(SRCROOT)/Library/MapleBacon/MapleBaconTests/Info.plist";
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_VERSION = 3.0;
+				SWIFT_SWIFT3_OBJC_INFERENCE = Default;
+				SWIFT_VERSION = 4.0;
 			};
 			name = Debug;
 		};
@@ -627,7 +644,8 @@
 				INFOPLIST_FILE = "$(SRCROOT)/Library/MapleBacon/MapleBaconTests/Info.plist";
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_VERSION = 3.0;
+				SWIFT_SWIFT3_OBJC_INFERENCE = Default;
+				SWIFT_VERSION = 4.0;
 			};
 			name = Release;
 		};
diff --git a/MapleBacon.xcodeproj/xcshareddata/xcschemes/MapleBacon-tvOS.xcscheme b/MapleBacon.xcodeproj/xcshareddata/xcschemes/MapleBacon-tvOS.xcscheme
index 4faa24e..b766230 100644
--- a/MapleBacon.xcodeproj/xcshareddata/xcschemes/MapleBacon-tvOS.xcscheme
+++ b/MapleBacon.xcodeproj/xcshareddata/xcschemes/MapleBacon-tvOS.xcscheme
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0800"
+   LastUpgradeVersion = "0900"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"
@@ -26,6 +26,7 @@
       buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      language = ""
       shouldUseLaunchSchemeArgsEnv = "YES">
       <Testables>
       </Testables>
@@ -36,6 +37,7 @@
       buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      language = ""
       launchStyle = "0"
       useCustomWorkingDirectory = "NO"
       ignoresPersistentStateOnLaunch = "NO"
diff --git a/MapleBacon.xcodeproj/xcshareddata/xcschemes/MapleBacon.xcscheme b/MapleBacon.xcodeproj/xcshareddata/xcschemes/MapleBacon.xcscheme
index 10bd755..6e307c0 100644
--- a/MapleBacon.xcodeproj/xcshareddata/xcschemes/MapleBacon.xcscheme
+++ b/MapleBacon.xcodeproj/xcshareddata/xcschemes/MapleBacon.xcscheme
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0800"
+   LastUpgradeVersion = "0900"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"
@@ -40,6 +40,7 @@
       buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      language = ""
       shouldUseLaunchSchemeArgsEnv = "YES">
       <Testables>
          <TestableReference
@@ -79,6 +80,7 @@
       buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      language = ""
       launchStyle = "0"
       useCustomWorkingDirectory = "NO"
       ignoresPersistentStateOnLaunch = "NO"
diff --git a/MapleBaconExample/MapleBaconExample.xcodeproj/project.pbxproj b/MapleBaconExample/MapleBaconExample.xcodeproj/project.pbxproj
index 41cad61..17d9bbf 100644
--- a/MapleBaconExample/MapleBaconExample.xcodeproj/project.pbxproj
+++ b/MapleBaconExample/MapleBaconExample.xcodeproj/project.pbxproj
@@ -227,12 +227,12 @@
 			attributes = {
 				LastSwiftMigration = 0700;
 				LastSwiftUpdateCheck = 0700;
-				LastUpgradeCheck = 0800;
+				LastUpgradeCheck = 0900;
 				ORGANIZATIONNAME = "Zalando SE";
 				TargetAttributes = {
 					F2AB726D1A40395200CCE62B = {
 						CreatedOnToolsVersion = 6.1.1;
-						LastSwiftMigration = 0800;
+						LastSwiftMigration = 0900;
 					};
 					F2AB72821A40395200CCE62B = {
 						CreatedOnToolsVersion = 6.1.1;
@@ -355,14 +355,20 @@
 				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_MODULES = YES;
 				CLANG_ENABLE_OBJC_ARC = YES;
+				CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;
 				CLANG_WARN_BOOL_CONVERSION = YES;
+				CLANG_WARN_COMMA = YES;
 				CLANG_WARN_CONSTANT_CONVERSION = YES;
 				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
 				CLANG_WARN_EMPTY_BODY = YES;
 				CLANG_WARN_ENUM_CONVERSION = YES;
 				CLANG_WARN_INFINITE_RECURSION = YES;
 				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
 				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
+				CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
+				CLANG_WARN_STRICT_PROTOTYPES = YES;
 				CLANG_WARN_SUSPICIOUS_MOVE = YES;
 				CLANG_WARN_UNREACHABLE_CODE = YES;
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
@@ -401,14 +407,20 @@
 				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_MODULES = YES;
 				CLANG_ENABLE_OBJC_ARC = YES;
+				CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;
 				CLANG_WARN_BOOL_CONVERSION = YES;
+				CLANG_WARN_COMMA = YES;
 				CLANG_WARN_CONSTANT_CONVERSION = YES;
 				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
 				CLANG_WARN_EMPTY_BODY = YES;
 				CLANG_WARN_ENUM_CONVERSION = YES;
 				CLANG_WARN_INFINITE_RECURSION = YES;
 				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
 				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
+				CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
+				CLANG_WARN_STRICT_PROTOTYPES = YES;
 				CLANG_WARN_SUSPICIOUS_MOVE = YES;
 				CLANG_WARN_UNREACHABLE_CODE = YES;
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
@@ -441,7 +453,8 @@
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = "de.zalando.$(PRODUCT_NAME:rfc1034identifier)";
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_VERSION = 3.0;
+				SWIFT_SWIFT3_OBJC_INFERENCE = Default;
+				SWIFT_VERSION = 4.0;
 			};
 			name = Debug;
 		};
@@ -454,7 +467,8 @@
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = "de.zalando.$(PRODUCT_NAME:rfc1034identifier)";
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_VERSION = 3.0;
+				SWIFT_SWIFT3_OBJC_INFERENCE = Default;
+				SWIFT_VERSION = 4.0;
 			};
 			name = Release;
 		};
diff --git a/MapleBaconExample/MapleBaconExample/AppDelegate.swift b/MapleBaconExample/MapleBaconExample/AppDelegate.swift
index 324d1f6..a8756ad 100644
--- a/MapleBaconExample/MapleBaconExample/AppDelegate.swift
+++ b/MapleBaconExample/MapleBaconExample/AppDelegate.swift
@@ -22,7 +22,7 @@ final class AppDelegate: UIResponder, UIApplicationDelegate {
 
         let darkColor = UIColor(red: 14 / 255, green: 43 / 255, blue: 57 / 255, alpha: 1)
         UINavigationBar.appearance().tintColor = darkColor
-        UINavigationBar.appearance().titleTextAttributes = [NSForegroundColorAttributeName: darkColor]
+        UINavigationBar.appearance().titleTextAttributes = [NSAttributedStringKey.foregroundColor: darkColor]
         UITabBar.appearance().barTintColor = darkColor
     }
 
diff --git a/README.md b/README.md
index 6d7eccc..3d9f54a 100644
--- a/README.md
+++ b/README.md
@@ -10,9 +10,9 @@ MapleBacon is a Swift image download and caching library. It is not currently in
 
 ## Requirements
 
-- Swift 3.1
+- Swift 4
 - iOS 8.0+
-- Xcode 8.0+
+- Xcode 9.0+
 
 ## Installation