diff --git a/DockProgress.xcodeproj/project.pbxproj b/DockProgress.xcodeproj/project.pbxproj
index 4b74a2a..c4e4a45 100644
--- a/DockProgress.xcodeproj/project.pbxproj
+++ b/DockProgress.xcodeproj/project.pbxproj
@@ -3,7 +3,7 @@
 	archiveVersion = 1;
 	classes = {
 	};
-	objectVersion = 48;
+	objectVersion = 50;
 	objects = {
 
 /* Begin PBXAggregateTarget section */
@@ -47,7 +47,7 @@
 
 /* Begin PBXFileReference section */
 		"DockProgress::DockProgress::Product" /* DockProgress.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; path = DockProgress.framework; sourceTree = BUILT_PRODUCTS_DIR; };
-		"DockProgress::DockProgressTests::Product" /* DockProgressTests.xctest */ = {isa = PBXFileReference; lastKnownFileType = file; path = DockProgressTests.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
+		"DockProgress::DockProgressTests::Product" /* DockProgressTests.xctest */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; path = DockProgressTests.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
 		E392EC532048876F00AB7097 /* util.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; lineEnding = 0; path = util.swift; sourceTree = "<group>"; usesTabs = 1; };
 		OBJ_12 /* DockProgressTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DockProgressTests.swift; sourceTree = "<group>"; };
 		OBJ_6 /* Package.swift */ = {isa = PBXFileReference; explicitFileType = sourcecode.swift; fileEncoding = 4; lineEnding = 0; path = Package.swift; sourceTree = "<group>"; usesTabs = 1; };
@@ -184,10 +184,10 @@
 		OBJ_1 /* Project object */ = {
 			isa = PBXProject;
 			attributes = {
-				LastUpgradeCheck = 9999;
+				LastUpgradeCheck = 0930;
 			};
 			buildConfigurationList = OBJ_2 /* Build configuration list for PBXProject "DockProgress" */;
-			compatibilityVersion = "Xcode 8.0";
+			compatibilityVersion = "Xcode 9.3";
 			developmentRegion = English;
 			hasScannedForEncodings = 0;
 			knownRegions = (
@@ -269,14 +269,17 @@
 		OBJ_24 /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
-				EMBEDDED_CONTENT_CONTAINS_SWIFT = YES;
+				ALWAYS_EMBED_SWIFT_STANDARD_LIBRARIES = YES;
 				FRAMEWORK_SEARCH_PATHS = (
 					"$(inherited)",
 					"$(PLATFORM_DIR)/Developer/Library/Frameworks",
 				);
 				HEADER_SEARCH_PATHS = "$(inherited)";
 				INFOPLIST_FILE = DockProgress.xcodeproj/DockProgressTests_Info.plist;
-				LD_RUNPATH_SEARCH_PATHS = "@loader_path/../Frameworks @loader_path/Frameworks";
+				LD_RUNPATH_SEARCH_PATHS = (
+					"@loader_path/../Frameworks",
+					"@loader_path/Frameworks",
+				);
 				OTHER_LDFLAGS = "$(inherited)";
 				OTHER_SWIFT_FLAGS = "$(inherited)";
 				SWIFT_VERSION = 4.0;
@@ -287,14 +290,17 @@
 		OBJ_25 /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
-				EMBEDDED_CONTENT_CONTAINS_SWIFT = YES;
+				ALWAYS_EMBED_SWIFT_STANDARD_LIBRARIES = YES;
 				FRAMEWORK_SEARCH_PATHS = (
 					"$(inherited)",
 					"$(PLATFORM_DIR)/Developer/Library/Frameworks",
 				);
 				HEADER_SEARCH_PATHS = "$(inherited)";
 				INFOPLIST_FILE = DockProgress.xcodeproj/DockProgressTests_Info.plist;
-				LD_RUNPATH_SEARCH_PATHS = "@loader_path/../Frameworks @loader_path/Frameworks";
+				LD_RUNPATH_SEARCH_PATHS = (
+					"@loader_path/../Frameworks",
+					"@loader_path/Frameworks",
+				);
 				OTHER_LDFLAGS = "$(inherited)";
 				OTHER_SWIFT_FLAGS = "$(inherited)";
 				SWIFT_VERSION = 4.0;
@@ -306,12 +312,38 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				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_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
+				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_IMPLICIT_RETAIN_SELF = YES;
+				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
+				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;
 				COMBINE_HIDPI_IMAGES = YES;
 				COPY_PHASE_STRIP = NO;
 				DEBUG_INFORMATION_FORMAT = dwarf;
 				DYLIB_INSTALL_NAME_BASE = "@rpath";
 				ENABLE_NS_ASSERTIONS = YES;
+				ENABLE_STRICT_OBJC_MSGSEND = YES;
+				ENABLE_TESTABILITY = YES;
+				GCC_NO_COMMON_BLOCKS = YES;
 				GCC_OPTIMIZATION_LEVEL = 0;
+				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
+				GCC_WARN_ABOUT_RETURN_TYPE = YES;
+				GCC_WARN_UNDECLARED_SELECTOR = YES;
+				GCC_WARN_UNINITIALIZED_AUTOS = YES;
+				GCC_WARN_UNUSED_FUNCTION = YES;
+				GCC_WARN_UNUSED_VARIABLE = YES;
 				MACOSX_DEPLOYMENT_TARGET = 10.12;
 				ONLY_ACTIVE_ARCH = YES;
 				OTHER_SWIFT_FLAGS = "-DXcode";
@@ -319,6 +351,7 @@
 				SDKROOT = macosx;
 				SUPPORTED_PLATFORMS = macosx;
 				SWIFT_ACTIVE_COMPILATION_CONDITIONS = SWIFT_PACKAGE;
+				SWIFT_COMPILATION_MODE = singlefile;
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
 				USE_HEADERMAP = NO;
 				VALID_ARCHS = x86_64;
@@ -373,18 +406,44 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				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_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
+				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_IMPLICIT_RETAIN_SELF = YES;
+				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
+				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;
 				COMBINE_HIDPI_IMAGES = YES;
 				COPY_PHASE_STRIP = YES;
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				DYLIB_INSTALL_NAME_BASE = "@rpath";
+				ENABLE_STRICT_OBJC_MSGSEND = YES;
+				GCC_NO_COMMON_BLOCKS = YES;
 				GCC_OPTIMIZATION_LEVEL = s;
+				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
+				GCC_WARN_ABOUT_RETURN_TYPE = YES;
+				GCC_WARN_UNDECLARED_SELECTOR = YES;
+				GCC_WARN_UNINITIALIZED_AUTOS = YES;
+				GCC_WARN_UNUSED_FUNCTION = YES;
+				GCC_WARN_UNUSED_VARIABLE = YES;
 				MACOSX_DEPLOYMENT_TARGET = 10.12;
 				OTHER_SWIFT_FLAGS = "-DXcode";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = macosx;
 				SUPPORTED_PLATFORMS = macosx;
 				SWIFT_ACTIVE_COMPILATION_CONDITIONS = SWIFT_PACKAGE;
-				SWIFT_OPTIMIZATION_LEVEL = "-Owholemodule";
+				SWIFT_COMPILATION_MODE = wholemodule;
+				SWIFT_OPTIMIZATION_LEVEL = "-O";
 				USE_HEADERMAP = NO;
 				VALID_ARCHS = x86_64;
 			};
diff --git a/DockProgress.xcodeproj/xcshareddata/xcschemes/DockProgress-Package.xcscheme b/DockProgress.xcodeproj/xcshareddata/xcschemes/DockProgress-Package.xcscheme
index b4db6f2..06f47f2 100644
--- a/DockProgress.xcodeproj/xcshareddata/xcschemes/DockProgress-Package.xcscheme
+++ b/DockProgress.xcodeproj/xcshareddata/xcschemes/DockProgress-Package.xcscheme
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "9999"
+   LastUpgradeVersion = "0930"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"
@@ -26,7 +26,6 @@
       buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
-      language = ""
       shouldUseLaunchSchemeArgsEnv = "YES">
       <Testables>
          <TestableReference
@@ -47,7 +46,6 @@
       buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
-      language = ""
       launchStyle = "0"
       useCustomWorkingDirectory = "NO"
       ignoresPersistentStateOnLaunch = "NO"
diff --git a/Package.swift b/Package.swift
index 27c18af..cfea27d 100644
--- a/Package.swift
+++ b/Package.swift
@@ -1,4 +1,4 @@
-// swift-tools-version:4.0
+// swift-tools-version:4.1
 import PackageDescription
 
 let package = Package(
diff --git a/readme.md b/readme.md
index 1b857e5..452a791 100644
--- a/readme.md
+++ b/readme.md
@@ -10,8 +10,8 @@ This package is used in production by the [Gifski app](https://github.com/sindre
 ## Requirements
 
 - macOS 10.12+
-- Xcode 9+
-- Swift 4+
+- Xcode 9.3+
+- Swift 4.1+
 
 
 ## Install