diff --git a/KYNavigationProgress/ProgressView.swift b/KYNavigationProgress/ProgressView.swift
index cd320f0..3e79204 100644
--- a/KYNavigationProgress/ProgressView.swift
+++ b/KYNavigationProgress/ProgressView.swift
@@ -16,9 +16,8 @@ internal final class ProgressView: UIView {
     
     internal var progress: Float = 0 {
         didSet {
-            guard let superview = superview else { return }
             progress = min(1, progress)
-            barWidthConstraint.constant = superview.frame.width * CGFloat(progress)
+            barWidthConstraint.constant = bounds.width * CGFloat(progress)
         }
     }
     
@@ -30,6 +29,13 @@ internal final class ProgressView: UIView {
     
     private let barWidthConstraint: NSLayoutConstraint
     
+    override var bounds: CGRect {
+        didSet {
+            let tmpProgress = progress
+            progress = tmpProgress
+        }
+    }
+    
     
     /* ====================================================================== */
     // MARK: - initializer
@@ -51,12 +57,6 @@ internal final class ProgressView: UIView {
         
         super.init(frame: frame)
         
-        NSNotificationCenter.defaultCenter().addObserver(
-            self,
-            selector: "deviceDidRotate:",
-            name: UIDeviceOrientationDidChangeNotification,
-            object: nil)
-        
         let leftConstraint = NSLayoutConstraint(
             item: bar,
             attribute: .Left,
@@ -97,21 +97,12 @@ internal final class ProgressView: UIView {
             bottomConstraint])
     }
     
-    deinit {
-        NSNotificationCenter.defaultCenter().removeObserver(
-            self,
-            name: UIDeviceOrientationDidChangeNotification,
-            object: nil)
-    }
-    
     
     /* ====================================================================== */
     // MARK: - Notification
     /* ====================================================================== */
     
     func deviceDidRotate(notification: NSNotification) {
-        let tmpProgress = progress
-        progress = tmpProgress
     }
     
     
diff --git a/KYNavigationProgress/UINavigationController+Progress.swift b/KYNavigationProgress/UINavigationController+Progress.swift
index 8273f8c..6dce16a 100644
--- a/KYNavigationProgress/UINavigationController+Progress.swift
+++ b/KYNavigationProgress/UINavigationController+Progress.swift
@@ -8,6 +8,8 @@
 
 import UIKit
 
+private let constraintIdentifier = "progressHeightConstraint"
+
 public extension UINavigationController {
     
     /* ====================================================================== */
@@ -18,12 +20,15 @@ public extension UINavigationController {
      Default is 2.0
     */
     public var progressHeight: CGFloat {
-        get { return progressView.frame.height }
+        get {
+            return navigationBar.constraints
+                .filter{ $0.identifier == constraintIdentifier }
+                .first?.constant ?? 0.2
+        }
         set {
-            var frame = progressView.frame
-            frame.size.height = newValue
-            frame.origin.y = navigationBar.frame.height - newValue
-            progressView.frame = frame
+            navigationBar.constraints
+                .filter{ $0.identifier == constraintIdentifier }
+                .first?.constant = newValue
         }
     }
     
@@ -63,7 +68,6 @@ public extension UINavigationController {
         }
         
         let defaultHeight = CGFloat(2)
-        
         let frame = CGRect(
             x: 0,
             y: navigationBar.frame.height - defaultHeight,
@@ -72,8 +76,32 @@ public extension UINavigationController {
         )
         let progressView = ProgressView(frame: frame)
         
+        progressView.translatesAutoresizingMaskIntoConstraints = false
+        
         navigationBar.addSubview(progressView)
         
+        let progressHeightConstraint = NSLayoutConstraint(
+            item: progressView,
+            attribute: .Height,
+            relatedBy: .Equal,
+            toItem: nil,
+            attribute: .NotAnAttribute,
+            multiplier: 1,
+            constant: defaultHeight)
+        progressHeightConstraint.identifier = constraintIdentifier
+        
+        navigationBar.addConstraint(progressHeightConstraint)
+        navigationBar.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat(
+            "H:|-0-[progressView]-0-|",
+            options: [],
+            metrics: nil,
+            views: ["progressView" : progressView]))
+        navigationBar.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat(
+            "V:[progressView]-0-|",
+            options: [],
+            metrics: nil,
+            views: ["progressView" : progressView]))
+        
         return progressView
     }
     
@@ -97,6 +125,7 @@ public extension UINavigationController {
      While progress is changed to 1.0, the bar will fade out. After that, progress will be 0.0.
     */
     public func finishProgress() {
+        progressView.bar.alpha = 1
         progressView.setProgress(1, animated: true)
         
         UIView.animateWithDuration(0.25,