diff --git a/src/Dock.Avalonia/Internal/DockControlState.cs b/src/Dock.Avalonia/Internal/DockControlState.cs
index 91fcf9392..3b90c213f 100644
--- a/src/Dock.Avalonia/Internal/DockControlState.cs
+++ b/src/Dock.Avalonia/Internal/DockControlState.cs
@@ -2,7 +2,6 @@
 using System.Collections.Generic;
 using Avalonia;
 using Avalonia.Controls;
-using Avalonia.Input;
 using Avalonia.VisualTree;
 using Dock.Avalonia.Controls;
 using Dock.Model.Core;
@@ -141,6 +140,11 @@ private void Execute(Point point, DockOperation operation, DragAction dragAction
         {
             if (sourceDockable is IDock dock)
             {
+                if (dock.ActiveDockable == null)
+                {
+                    return;
+                }
+
                 sourceDockable = dock.ActiveDockable;
             }
 
diff --git a/tests/Dock.Avalonia.UnitTests/Controls/ProportionalStackPanelTests.cs b/tests/Dock.Avalonia.UnitTests/Controls/ProportionalStackPanelTests.cs
index cd705fcbb..b997a3d60 100644
--- a/tests/Dock.Avalonia.UnitTests/Controls/ProportionalStackPanelTests.cs
+++ b/tests/Dock.Avalonia.UnitTests/Controls/ProportionalStackPanelTests.cs
@@ -60,7 +60,7 @@ public void Lays_Out_Children_Vertical()
         Assert.Equal(new Rect(0, 152, 100, 148), target.Children[2].Bounds);
     }
 
-    private static IEnumerable<object[]> GetBorderTestsData()
+    public static IEnumerable<object[]> GetBorderTestsData()
     {
         yield return [0.5, 604, 300, 300];
         yield return [0.25, 604, 150, 450];
diff --git a/tests/Dock.Model.Mvvm.UnitTests/FactoryTests.cs b/tests/Dock.Model.Mvvm.UnitTests/FactoryTests.cs
index b8fa46692..0c3987990 100644
--- a/tests/Dock.Model.Mvvm.UnitTests/FactoryTests.cs
+++ b/tests/Dock.Model.Mvvm.UnitTests/FactoryTests.cs
@@ -22,7 +22,7 @@ public void CreateList_Creates_ReactiveList_Empty()
         var actual = factory.CreateList<IDockable>();
         Assert.NotNull(actual);
         Assert.IsType<ObservableCollection<IDockable>>(actual);
-        Assert.Equal(0, actual.Count);
+        Assert.Empty(actual);
     }
 
     [Fact]
diff --git a/tests/Dock.Model.ReactiveUI.UnitTests/FactoryTests.cs b/tests/Dock.Model.ReactiveUI.UnitTests/FactoryTests.cs
index 61852a3f7..289c1c78b 100644
--- a/tests/Dock.Model.ReactiveUI.UnitTests/FactoryTests.cs
+++ b/tests/Dock.Model.ReactiveUI.UnitTests/FactoryTests.cs
@@ -22,7 +22,7 @@ public void CreateList_Creates_ReactiveList_Empty()
         var actual = factory.CreateList<IDockable>();
         Assert.NotNull(actual);
         Assert.IsType<ObservableCollection<IDockable>>(actual);
-        Assert.Equal(0, actual.Count);
+        Assert.Empty(actual);
     }
 
     [Fact]
@@ -101,4 +101,4 @@ public void CreateLayout_Creates_RootDock()
 
 public class TestFactory : Factory
 {
-}
\ No newline at end of file
+}