diff --git a/src/Markup/Avalonia.Markup/ControlLocator.cs b/src/Markup/Avalonia.Markup/ControlLocator.cs
index 41851ca288..300da8a739 100644
--- a/src/Markup/Avalonia.Markup/ControlLocator.cs
+++ b/src/Markup/Avalonia.Markup/ControlLocator.cs
@@ -121,7 +121,7 @@ namespace Avalonia.Markup
 
             var detached = Observable.FromEventPattern<LogicalTreeAttachmentEventArgs>(
                 x => relativeTo.DetachedFromLogicalTree += x,
-                x => relativeTo.DetachedFromLogicalTree += x)
+                x => relativeTo.DetachedFromLogicalTree -= x)
                 .Select(x => false);
 
             return attached.Merge(detached).Select(isAttachedToLogicalTree =>