diff --git a/source/Components/AvalonDock/Controls/DropTarget.cs b/source/Components/AvalonDock/Controls/DropTarget.cs
index c1c31ca3..9694c39d 100644
--- a/source/Components/AvalonDock/Controls/DropTarget.cs
+++ b/source/Components/AvalonDock/Controls/DropTarget.cs
@@ -121,7 +121,8 @@ public void Drop(LayoutFloatingWindow floatingWindow)
 				var fwAsDocument = floatingWindow as LayoutDocumentFloatingWindow;
 				this.Drop(fwAsDocument);
 			}
-
+			if (currentActiveContent == null)
+				return;
 			Dispatcher.BeginInvoke(new Action(() =>
 				{
 					currentActiveContent.IsSelected = false;
@@ -149,4 +150,4 @@ public void DragLeave()
 
 		#endregion Public Methods
 	}
-}
\ No newline at end of file
+}