diff --git a/Makefile b/Makefile
index b7009b84..c548594a 100644
--- a/Makefile
+++ b/Makefile
@@ -1,10 +1,11 @@
 VERSION := $(shell /usr/libexec/PlistBuddy -c "Print CFBundleShortVersionString" WeaverDI.xcodeproj/WeaverCodeGen_Info.plist)
-PREFIX = /usr/local
+PREFIX=/usr/local
+SWIFT_BUILD_FLAGS=--configuration release
 
 .PHONY: clean build install package generate_sources codecov
 
 build:
-	$(call build)
+	@swift build --disable-sandbox $(SWIFT_BUILD_FLAGS)
 
 generate_sources:
 	bash -c "(command -v sourcery && sourcery) || echo 'warning: Sourcery is not installed'"
@@ -12,29 +13,22 @@ generate_sources:
 clean:
 	rm -rf .build
 
-install:
-	$(call build)
+install: build
 	$(call install_files,$(PREFIX)) 
 
 uninstall:
 	rm "$(PREFIX)/bin/weaver"
 	rm -rf "$(PREFIX)/share/weaver"
 
-package:
-	$(call build)
+package: build
 	$(call install_files,./build/package/weaver)
 	cd ./build/package/ && zip -r ../../weaver-$(VERSION).zip ./weaver
 
-codecov:
-	$(call build)
+codecov: build
 	xcodebuild test -scheme Tests -enableCodeCoverage YES
 	bash -c "bash <(curl -s https://codecov.io/bash) -J Weaver -t eaa7c4af-5ca2-4e08-8f07-38a44671e5e0"
 	rm *.coverage.txt
 
-define build
-	@swift build --disable-sandbox --configuration release
-endef
-
 define install_files
 	install -d $(1)/bin
 	install -d $(1)/share/weaver/Resources
diff --git a/Package.resolved b/Package.resolved
index e54015ba..86d18175 100644
--- a/Package.resolved
+++ b/Package.resolved
@@ -78,8 +78,8 @@
         "repositoryURL": "https://github.com/jpsim/SourceKitten.git",
         "state": {
           "branch": null,
-          "revision": "b6b10419ee439167ba6f7bd928ad30754ff5eb5d",
-          "version": "0.20.0"
+          "revision": "7c09176766d4bbc5da377ad857953fb49510a6aa",
+          "version": "0.21.0"
         }
       },
       {
diff --git a/Package.swift b/Package.swift
index 1b861f09..990d69ea 100644
--- a/Package.swift
+++ b/Package.swift
@@ -1,4 +1,4 @@
-// swift-tools-version:4.1
+// swift-tools-version:4.0
 import PackageDescription
 
 let package = Package(
@@ -7,9 +7,9 @@ let package = Package(
         .library(name: "WeaverDI", targets: ["WeaverDI"])
     ],
     dependencies: [
-        .package(url: "https://github.com/jpsim/SourceKitten.git", from: "0.19.1"),
+        .package(url: "https://github.com/jpsim/SourceKitten.git", from: "0.21.0"),
         .package(url: "https://github.com/kylef/Commander.git", from: "0.6.0"),
-        .package(url: "https://github.com/kylef/Stencil.git", from: "0.10.1")
+        .package(url: "https://github.com/kylef/Stencil.git", from: "0.11.0")
     ],
     targets: [
         .target(name: "WeaverDI"),
diff --git a/Sources/WeaverCodeGen/shim-swift-4.1.swift b/Sources/WeaverCodeGen/shim-swift-4.1.swift
new file mode 100644
index 00000000..a4164882
--- /dev/null
+++ b/Sources/WeaverCodeGen/shim-swift-4.1.swift
@@ -0,0 +1,17 @@
+//
+//  shim-swift-4.2.swift
+//  WeaverCodeGen
+//
+//  Created by Théophane Rupin on 6/3/18.
+//
+
+import Foundation
+
+#if swift(>=4.1)
+#else
+extension Collection {
+    public func compactMap<ElementOfResult>(_ transform: (Element) throws -> ElementOfResult?) rethrows -> [ElementOfResult] {
+        return try flatMap(transform)
+    }
+}
+#endif
diff --git a/WeaverDI.xcodeproj/project.pbxproj b/WeaverDI.xcodeproj/project.pbxproj
index 38a9624b..8def95b3 100644
--- a/WeaverDI.xcodeproj/project.pbxproj
+++ b/WeaverDI.xcodeproj/project.pbxproj
@@ -22,6 +22,7 @@
 /* End PBXAggregateTarget section */
 
 /* Begin PBXBuildFile section */
+		19F3CD6820C43F32007C3076 /* shim-swift-4.1.swift in Sources */ = {isa = PBXBuildFile; fileRef = 19F3CD6720C43F32007C3076 /* shim-swift-4.1.swift */; };
 		OBJ_199 /* Package.swift in Sources */ = {isa = PBXBuildFile; fileRef = OBJ_6 /* Package.swift */; };
 		OBJ_205 /* Package.swift in Sources */ = {isa = PBXBuildFile; fileRef = OBJ_57 /* Package.swift */; };
 		OBJ_211 /* Package.swift in Sources */ = {isa = PBXBuildFile; fileRef = OBJ_78 /* Package.swift */; };
@@ -457,6 +458,7 @@
 /* End PBXContainerItemProxy section */
 
 /* Begin PBXFileReference section */
+		19F3CD6720C43F32007C3076 /* shim-swift-4.1.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "shim-swift-4.1.swift"; sourceTree = "<group>"; };
 		"Commander::Commander::Product" /* Commander.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; path = Commander.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		OBJ_10 /* Dependencies.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Dependencies.swift; sourceTree = "<group>"; };
 		OBJ_100 /* Reporter.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Reporter.swift; sourceTree = "<group>"; };
@@ -885,6 +887,7 @@
 		OBJ_17 /* WeaverCodeGen */ = {
 			isa = PBXGroup;
 			children = (
+				19F3CD6720C43F32007C3076 /* shim-swift-4.1.swift */,
 				OBJ_18 /* AccessLevel.swift */,
 				OBJ_19 /* AutoEquatable.generated.swift */,
 				OBJ_20 /* AutoHashable.generated.swift */,
@@ -1657,6 +1660,7 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 0;
 			files = (
+				19F3CD6820C43F32007C3076 /* shim-swift-4.1.swift in Sources */,
 				OBJ_329 /* AccessLevel.swift in Sources */,
 				OBJ_330 /* AutoEquatable.generated.swift in Sources */,
 				OBJ_331 /* AutoHashable.generated.swift in Sources */,