diff --git a/Package.swift b/Package.swift
index 2365757..b69602b 100644
--- a/Package.swift
+++ b/Package.swift
@@ -1,19 +1,21 @@
-// swift-tools-version:4.0
+// swift-tools-version:5.1
 // Generated automatically by Perfect Assistant
 // Date: 2018-05-31 18:31:13 +0000
 import PackageDescription
 
 let package = Package(
 	name: "PerfectMustache",
+	platforms: [
+		.macOS(.v10_15)
+	],
 	products: [
 		.library(name: "PerfectMustache", targets: ["PerfectMustache"])
 	],
 	dependencies: [
-		.package(url: "https://github.com/PerfectlySoft/Perfect-Thread.git", from: "3.0.0"),
-		.package(url: "https://github.com/PerfectlySoft/PerfectLib.git", from: "3.0.0"),
+		.package(url: "https://github.com/PerfectlySoft/PerfectLib.git", from: "4.0.0"),
 	],
 	targets: [
-		.target(name: "PerfectMustache", dependencies: ["PerfectThread", "PerfectLib"]),
+		.target(name: "PerfectMustache", dependencies: ["PerfectLib"]),
 		.testTarget(name: "PerfectMustacheTests", dependencies: ["PerfectMustache"])
 	]
 )
diff --git a/Sources/PerfectMustache/Mustache.swift b/Sources/PerfectMustache/Mustache.swift
index d60d13c..fcb8d33 100644
--- a/Sources/PerfectMustache/Mustache.swift
+++ b/Sources/PerfectMustache/Mustache.swift
@@ -17,31 +17,29 @@
 //===----------------------------------------------------------------------===//
 //
 
-import PerfectThread
 import PerfectLib
 import Foundation
 
 let mustacheExtension = "mustache"
 
 private var mustacheTemplateCache = [String: (Int, MustacheTemplate)]()
-private let mustacheTemplateCacheLock = Threading.RWLock()
+private let mustacheTemplateCacheQueue = DispatchQueue(label: "mustacheTemplateCache", attributes: .concurrent)
 
 private func getTemplateFromCache(_ path: String) throws -> MustacheTemplate {
 	let file = File(path)
-	var template: MustacheTemplate?
 	let modDate = file.modificationTime
-	
-	mustacheTemplateCacheLock.doWithReadLock {
+	var template: MustacheTemplate? = mustacheTemplateCacheQueue.sync {
 		if let fnd = mustacheTemplateCache[path], fnd.0 == modDate {
-			template = fnd.1.clone() as? MustacheTemplate
+			return fnd.1.clone() as? MustacheTemplate
 		}
+		return nil
 	}
 	if let templateW = template?.clone() as? MustacheTemplate {
 		return templateW
 	}
-	try mustacheTemplateCacheLock.doWithWriteLock {
+	template = try mustacheTemplateCacheQueue.sync(flags: .barrier) {
 		if let fnd = mustacheTemplateCache[path], fnd.0 == modDate {
-			template = fnd.1.clone() as? MustacheTemplate
+			return fnd.1.clone() as? MustacheTemplate
 		} else {
 			try file.open()
 			defer { file.close() }
@@ -51,7 +49,7 @@ private func getTemplateFromCache(_ path: String) throws -> MustacheTemplate {
 			let str = UTF8Encoding.encode(bytes: bytes)
 			let templateW = try parser.parse(string: str)
 			mustacheTemplateCache[path] = (modDate, templateW)
-			template = templateW.clone() as? MustacheTemplate
+			return templateW.clone() as? MustacheTemplate
 		}
 	}
 	guard let templateW = template else {