diff --git a/TZStackView/TZStackView.swift b/TZStackView/TZStackView.swift
index 2fd77a8..7551c0b 100755
--- a/TZStackView/TZStackView.swift
+++ b/TZStackView/TZStackView.swift
@@ -31,11 +31,23 @@ public class TZStackView: UIView {
         }
     }
     
-    public var alignment: TZStackViewAlignment = .Fill
+    public var alignment: TZStackViewAlignment = .Fill {
+        didSet {
+            setNeedsUpdateConstraints()
+        }
+    }
 
-    public var spacing: CGFloat = 0
+    public var spacing: CGFloat = 0 {
+        didSet {
+            setNeedsUpdateConstraints()
+        }
+    }
     
-    public var layoutMarginsRelativeArrangement = false
+    public var layoutMarginsRelativeArrangement = false {
+        didSet {
+            setNeedsUpdateConstraints()
+        }
+    }
 
     public private(set) var arrangedSubviews: [UIView] = [] {
         didSet {
diff --git a/TZStackViewDemo/ViewController.swift b/TZStackViewDemo/ViewController.swift
index 482cd17..6dcf6f2 100644
--- a/TZStackViewDemo/ViewController.swift
+++ b/TZStackViewDemo/ViewController.swift
@@ -159,7 +159,6 @@ class ViewController: UIViewController {
         default:
             tzStackView.alignment = .FirstBaseline
         }
-        tzStackView.setNeedsUpdateConstraints()
     }
 
     func distributionChanged(sender: UISegmentedControl) {