From 70f9554518d486366c6c6f66f0e61075d18766c0 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Mon, 6 Nov 2017 23:37:03 +0100
Subject: [PATCH] Fixed #1255.

---
 src/Avalonia.Controls/Classes.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/Classes.cs b/src/Avalonia.Controls/Classes.cs
index c897e86697..613273d5c7 100644
--- a/src/Avalonia.Controls/Classes.cs
+++ b/src/Avalonia.Controls/Classes.cs
@@ -179,7 +179,7 @@ namespace Avalonia.Controls
             {
                 ThrowIfPseudoclass(name, "removed");
 
-                if (!Contains(name))
+                if (Contains(name))
                 {
                     c.Add(name);
                 }