diff --git a/src/Dock.Model.Avalonia/Factory.cs b/src/Dock.Model.Avalonia/Factory.cs
index e28916f4..19317444 100644
--- a/src/Dock.Model.Avalonia/Factory.cs
+++ b/src/Dock.Model.Avalonia/Factory.cs
@@ -50,7 +50,13 @@ public Factory()
     public override IList<T> CreateList<T>(params T[] items) => new AvaloniaList<T>(items);
 
     /// <inheritdoc/>
-    public override IRootDock CreateRootDock() => new RootDock();
+    public override IRootDock CreateRootDock() => new RootDock
+    {
+        LeftPinnedDockables = CreateList<IDockable>(), 
+        RightPinnedDockables = CreateList<IDockable>(),
+        TopPinnedDockables = CreateList<IDockable>(),
+        BottomPinnedDockables = CreateList<IDockable>()
+    };
 
     /// <inheritdoc/>
     public override IProportionalDock CreateProportionalDock() => new ProportionalDock();
diff --git a/src/Dock.Model.Mvvm/Factory.cs b/src/Dock.Model.Mvvm/Factory.cs
index d1fdd51a..cab6cac3 100644
--- a/src/Dock.Model.Mvvm/Factory.cs
+++ b/src/Dock.Model.Mvvm/Factory.cs
@@ -43,7 +43,13 @@ public Factory()
     public override IList<T> CreateList<T>(params T[] items) => new ObservableCollection<T>(items);
 
     /// <inheritdoc/>
-    public override IRootDock CreateRootDock() => new RootDock();
+    public override IRootDock CreateRootDock() => new RootDock
+    {
+        LeftPinnedDockables = CreateList<IDockable>(), 
+        RightPinnedDockables = CreateList<IDockable>(),
+        TopPinnedDockables = CreateList<IDockable>(),
+        BottomPinnedDockables = CreateList<IDockable>()
+    };
 
     /// <inheritdoc/>
     public override IProportionalDock CreateProportionalDock() => new ProportionalDock();
diff --git a/src/Dock.Model.ReactiveUI/Factory.cs b/src/Dock.Model.ReactiveUI/Factory.cs
index fbd5120d..dbead5d2 100644
--- a/src/Dock.Model.ReactiveUI/Factory.cs
+++ b/src/Dock.Model.ReactiveUI/Factory.cs
@@ -43,7 +43,13 @@ public Factory()
     public override IList<T> CreateList<T>(params T[] items) => new ObservableCollection<T>(items);
 
     /// <inheritdoc/>
-    public override IRootDock CreateRootDock() => new RootDock();
+    public override IRootDock CreateRootDock() => new RootDock
+    {
+        LeftPinnedDockables = CreateList<IDockable>(), 
+        RightPinnedDockables = CreateList<IDockable>(),
+        TopPinnedDockables = CreateList<IDockable>(),
+        BottomPinnedDockables = CreateList<IDockable>()
+    };
 
     /// <inheritdoc/>
     public override IProportionalDock CreateProportionalDock() => new ProportionalDock();
@@ -65,4 +71,4 @@ public Factory()
 
     /// <inheritdoc/>
     public override IRootDock CreateLayout() => CreateRootDock();
-}
\ No newline at end of file
+}