diff --git a/src/Libraries/AvalonDock/AvalonDock/ManagedContent.cs b/src/Libraries/AvalonDock/AvalonDock/ManagedContent.cs
index 1259179fe0..501ac136bd 100644
--- a/src/Libraries/AvalonDock/AvalonDock/ManagedContent.cs
+++ b/src/Libraries/AvalonDock/AvalonDock/ManagedContent.cs
@@ -337,7 +337,9 @@ namespace AvalonDock
 
         protected virtual void OnDragMouseLeave(object sender, MouseEventArgs e)
         {
-            if (!e.Handled && isMouseDown && e.LeftButton == MouseButtonState.Pressed && Manager != null)
+        	// The MouseLeave event can occur if the managed content was closed while the user held the left mouse button pressed.
+        	// In that case, this.IsLoaded will be false and we won't handle the event
+            if (!e.Handled && isMouseDown && e.LeftButton == MouseButtonState.Pressed && Manager != null && this.IsLoaded)
             {
                 if (!IsMouseCaptured)
                 {