diff --git a/Source/PullToRefreshView.swift b/Source/PullToRefreshView.swift
index 28658f7..c850c94 100755
--- a/Source/PullToRefreshView.swift
+++ b/Source/PullToRefreshView.swift
@@ -7,6 +7,15 @@
 //
 import UIKit
 
+/*
+ Fix: Simultaneous access to memory due to KVO
+
+ For more information regarding this global variable follow the followinf links:
+ 1. https://developer.apple.com/swift/blog/?id=6
+ 2. http://michael-brown.net/2017/swift-and-kvo-context-variables/
+ */
+private var kvoContext = "PullToRefreshKVOContext"
+
 open class PullToRefreshView: UIView {
     enum PullToRefreshState {
         case pulling
@@ -19,14 +28,13 @@ open class PullToRefreshView: UIView {
     // MARK: Variables
     let contentOffsetKeyPath = "contentOffset"
     let contentSizeKeyPath = "contentSize"
-    var kvoContext = "PullToRefreshKVOContext"
     
     fileprivate var options: PullToRefreshOption
     fileprivate var backgroundView: UIView
     fileprivate var arrow: UIImageView
     fileprivate var indicator: UIActivityIndicatorView
     fileprivate var scrollViewInsets: UIEdgeInsets = UIEdgeInsets.zero
-    fileprivate var refreshCompletion: ((Void) -> Void)?
+    fileprivate var refreshCompletion: (() -> Void)?
     fileprivate var pull: Bool = true
     
     fileprivate var positionY:CGFloat = 0 {
@@ -78,7 +86,7 @@ open class PullToRefreshView: UIView {
         fatalError("init(coder:) has not been implemented")
     }
     
-    public init(options: PullToRefreshOption, frame: CGRect, refreshCompletion :((Void) -> Void)?, down:Bool=true) {
+    public init(options: PullToRefreshOption, frame: CGRect, refreshCompletion :(() -> Void)?, down:Bool=true) {
         self.options = options
         self.refreshCompletion = refreshCompletion
 
@@ -262,7 +270,7 @@ open class PullToRefreshView: UIView {
     fileprivate func arrowRotation() {
         UIView.animate(withDuration: 0.2, delay: 0, options:[], animations: {
             // -0.0000001 for the rotation direction control
-            self.arrow.transform = CGAffineTransform(rotationAngle: CGFloat(M_PI-0.0000001))
+            self.arrow.transform = CGAffineTransform(rotationAngle: CGFloat(Double.pi-0.0000001))
         }, completion:nil)
     }
     
diff --git a/Source/UIScrollViewExtension.swift b/Source/UIScrollViewExtension.swift
index 249fe52..6c1641d 100755
--- a/Source/UIScrollViewExtension.swift
+++ b/Source/UIScrollViewExtension.swift
@@ -14,14 +14,14 @@ public extension UIScrollView {
         return pullToRefreshView as? PullToRefreshView
     }
     
-    public func addPullRefresh(options: PullToRefreshOption = PullToRefreshOption(), refreshCompletion :((Void) -> Void)?) {
+    public func addPullRefresh(options: PullToRefreshOption = PullToRefreshOption(), refreshCompletion :(() -> Void)?) {
         let refreshViewFrame = CGRect(x: 0, y: -PullToRefreshConst.height, width: self.frame.size.width, height: PullToRefreshConst.height)
         let refreshView = PullToRefreshView(options: options, frame: refreshViewFrame, refreshCompletion: refreshCompletion)
         refreshView.tag = PullToRefreshConst.pullTag
         addSubview(refreshView)
     }
     
-    public func addPushRefresh(options: PullToRefreshOption = PullToRefreshOption(), refreshCompletion :((Void) -> Void)?) {
+    public func addPushRefresh(options: PullToRefreshOption = PullToRefreshOption(), refreshCompletion :(() -> Void)?) {
         let refreshViewFrame = CGRect(x: 0, y: contentSize.height, width: self.frame.size.width, height: PullToRefreshConst.height)
         let refreshView = PullToRefreshView(options: options, frame: refreshViewFrame, refreshCompletion: refreshCompletion,down: false)
         refreshView.tag = PullToRefreshConst.pushTag