diff --git a/.gitignore b/.gitignore
index 00b75fa..de34bb1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,3 +6,4 @@ xcuserdata/
 Package.pins
 Package.resolved
 Packages/
+.swiftpm
\ No newline at end of file
diff --git a/Package.swift b/Package.swift
index 5413dfe..305f4b1 100644
--- a/Package.swift
+++ b/Package.swift
@@ -3,11 +3,11 @@ import PackageDescription
 
 let package = Package(
 	name: "CwlUtils",
-   products: [
-   	.library(name: "CwlUtils", type: .dynamic, targets: ["CwlUtils"]),
+	products: [
+		.library(name: "CwlUtils", type: .dynamic, targets: ["CwlUtils"]),
 	],
 	dependencies: [
-		.package(url: "https://github.com/mattgallagher/CwlPreconditionTesting.git", from: "1.2.0"),
+		.package(url: "https://github.com/mattgallagher/CwlPreconditionTesting.git", from: "2.0.0"),
 	],
 	targets: [
 		.target(
diff --git a/Sources/CwlUtils/CwlDeque.swift b/Sources/CwlUtils/CwlDeque.swift
index 0c2beac..52ea6b9 100644
--- a/Sources/CwlUtils/CwlDeque.swift
+++ b/Sources/CwlUtils/CwlDeque.swift
@@ -398,7 +398,7 @@ public struct Deque<T>: RandomAccessCollection, MutableCollection, RangeReplacea
 }
 
 // Internal state for the Deque
-private struct DequeHeader {
+public struct DequeHeader {
 	var offset: Int
 	var count: Int
 	var capacity: Int
@@ -455,7 +455,7 @@ private struct HeapObject {
 // storage and then using raw pointer offsets into self to access contents
 // (avoiding the ManagedBufferPointer accessors which are a performance problem
 // in Swift 3).
-private final class DequeBuffer<T>: ManagedBuffer<DequeHeader, T> {
+public final class DequeBuffer<T>: ManagedBuffer<DequeHeader, T> {
 	#if true
 		private static var headerOffset: Int {
 			return Int(roundUp(UInt(MemoryLayout<HeapObject>.size), toAlignment: MemoryLayout<DequeHeader>.alignment))