From ccf7f4a1296b83b3b9d8626e4cc66f2a9e194134 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sat, 19 Sep 2015 18:23:45 +0200
Subject: [PATCH] Ensure sender of correct type in AddClassHandler.

---
 src/Perspex.Base/PerspexObjectExtensions.cs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/Perspex.Base/PerspexObjectExtensions.cs b/src/Perspex.Base/PerspexObjectExtensions.cs
index c690d30996..cc595e0130 100644
--- a/src/Perspex.Base/PerspexObjectExtensions.cs
+++ b/src/Perspex.Base/PerspexObjectExtensions.cs
@@ -26,7 +26,13 @@ namespace Perspex
             Action<TTarget, PerspexPropertyChangedEventArgs> action)
             where TTarget : PerspexObject
         {
-            return observable.Subscribe(e => action((TTarget)e.Sender, e));
+            return observable.Subscribe(e =>
+            {
+                if (e.Sender is TTarget)
+                {
+                    action((TTarget)e.Sender, e);
+                }
+            });
         }
 
         /// <summary>