diff --git a/samples/DockMvvmSample/Views/ProportionalStackPanelView.axaml b/samples/DockMvvmSample/Views/ProportionalStackPanelView.axaml
index 9e07a74fb..f1b182926 100644
--- a/samples/DockMvvmSample/Views/ProportionalStackPanelView.axaml
+++ b/samples/DockMvvmSample/Views/ProportionalStackPanelView.axaml
@@ -14,8 +14,8 @@
     <TabControl>
       <TabItem Header="Default">
         <ProportionalStackPanel Orientation="Horizontal">
-          <ProportionalStackPanel ProportionalStackPanelSplitter.Proportion="0.5">
-            <Rectangle Fill="Red" ProportionalStackPanelSplitter.Proportion="0.5" />
+          <ProportionalStackPanel ProportionalStackPanel.Proportion="0.5">
+            <Rectangle Fill="Red" ProportionalStackPanel.Proportion="0.5" />
             <ProportionalStackPanelSplitter />
             <Rectangle Fill="Green" />
             <ProportionalStackPanelSplitter />
@@ -35,7 +35,7 @@
             <ProportionalStackPanelSplitter />
             <Rectangle Fill="Blue" />
             <ProportionalStackPanelSplitter />
-            <Rectangle Fill="Red" ProportionalStackPanelSplitter.Proportion="0.5" />
+            <Rectangle Fill="Red" ProportionalStackPanel.Proportion="0.5" />
           </ProportionalStackPanel>
         </ProportionalStackPanel>
       </TabItem>
diff --git a/src/Dock.Avalonia/Controls/DockDockControl.axaml b/src/Dock.Avalonia/Controls/DockDockControl.axaml
index d647abd88..30acd1bec 100644
--- a/src/Dock.Avalonia/Controls/DockDockControl.axaml
+++ b/src/Dock.Avalonia/Controls/DockDockControl.axaml
@@ -8,9 +8,6 @@
 
   <ControlTheme x:Key="{x:Type DockDockControl}" TargetType="DockDockControl">
 
-    <Setter Property="(ProportionalStackPanelSplitter.Proportion)" Value="{Binding Proportion}" x:DataType="core:IDock" />
-    <Setter Property="(ProportionalStackPanelSplitter.IsEmpty)" Value="{Binding IsEmpty}" x:DataType="core:IDock" />
-
     <Setter Property="Template">
       <ControlTemplate>
         <DockableControl TrackingMode="Visible">
diff --git a/src/Dock.Avalonia/Controls/DocumentDockControl.axaml b/src/Dock.Avalonia/Controls/DocumentDockControl.axaml
index ac76ef257..505791a5e 100644
--- a/src/Dock.Avalonia/Controls/DocumentDockControl.axaml
+++ b/src/Dock.Avalonia/Controls/DocumentDockControl.axaml
@@ -7,13 +7,9 @@
 
   <ControlTheme x:Key="{x:Type DocumentDockControl}" TargetType="DocumentDockControl">
 
-    <Setter Property="(ProportionalStackPanelSplitter.Proportion)" Value="{Binding Proportion}" x:DataType="core:IDock" />
-    <Setter Property="(ProportionalStackPanelSplitter.IsEmpty)" Value="{Binding IsEmpty}" x:DataType="core:IDock" />
-
     <Setter Property="Template">
       <ControlTemplate>
-        <DockableControl TrackingMode="Visible"
-                         ProportionalStackPanelSplitter.Proportion="{Binding Proportion}">
+        <DockableControl TrackingMode="Visible">
           <DocumentControl IsActive="{Binding IsActive}" />
         </DockableControl>
       </ControlTemplate>
diff --git a/src/Dock.Avalonia/Controls/ProportionalDockControl.axaml b/src/Dock.Avalonia/Controls/ProportionalDockControl.axaml
index 20f3e25a4..6859ab333 100644
--- a/src/Dock.Avalonia/Controls/ProportionalDockControl.axaml
+++ b/src/Dock.Avalonia/Controls/ProportionalDockControl.axaml
@@ -8,17 +8,14 @@
 
   <ControlTheme x:Key="{x:Type ProportionalDockControl}" TargetType="ProportionalDockControl">
 
-    <Setter Property="(ProportionalStackPanelSplitter.Proportion)" Value="{Binding Proportion}" x:DataType="core:IDock" />
-    <Setter Property="(ProportionalStackPanelSplitter.IsEmpty)" Value="{Binding IsEmpty}" x:DataType="core:IDock" />
-
     <Setter Property="Template">
       <ControlTemplate>
-        <DockableControl TrackingMode="Visible"
-                         ProportionalStackPanelSplitter.Proportion="{Binding Proportion}">
+        <DockableControl TrackingMode="Visible">
           <ItemsControl ItemsSource="{Binding VisibleDockables}">
             <ItemsControl.Styles>
-              <Style Selector="ItemsControl > ContentPresenter > :is(core|IDock)" x:DataType="core:IDock">
-                <Setter Property="(ProportionalStackPanelSplitter.Proportion)" Value="{Binding Proportion}" />
+              <Style Selector="ItemsControl > ContentPresenter">
+                <Setter x:DataType="core:IDock" Property="(ProportionalStackPanel.Proportion)" Value="{Binding Proportion}" />
+                <Setter x:DataType="core:IDock" Property="(ProportionalStackPanel.IsEmpty)" Value="{Binding IsEmpty}" />
               </Style>
             </ItemsControl.Styles>
             <ItemsControl.ItemsPanel>
diff --git a/src/Dock.Avalonia/Controls/ProportionalStackPanel.cs b/src/Dock.Avalonia/Controls/ProportionalStackPanel.cs
index 85a1bc139..6a7b8e6a3 100644
--- a/src/Dock.Avalonia/Controls/ProportionalStackPanel.cs
+++ b/src/Dock.Avalonia/Controls/ProportionalStackPanel.cs
@@ -4,6 +4,7 @@
 using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Controls.Presenters;
+using Avalonia.Data;
 using Avalonia.Layout;
 
 namespace Dock.Avalonia.Controls;
@@ -28,6 +29,58 @@ public Orientation Orientation
         set => SetValue(OrientationProperty, value);
     }
 
+    /// <summary>
+    /// Defines the Proportion attached property.
+    /// </summary>
+    public static readonly AttachedProperty<double> ProportionProperty =
+        AvaloniaProperty.RegisterAttached<ProportionalStackPanel, Control, double>("Proportion", double.NaN, false, BindingMode.TwoWay);
+
+    /// <summary>
+    /// Gets the value of the Proportion attached property on the specified control.
+    /// </summary>
+    /// <param name="control">The control.</param>
+    /// <returns>The Proportion attached property.</returns>
+    public static double GetProportion(AvaloniaObject control)
+    {
+        return control.GetValue(ProportionProperty);
+    }
+
+    /// <summary>
+    /// Sets the value of the Proportion attached property on the specified control.
+    /// </summary>
+    /// <param name="control">The control.</param>
+    /// <param name="value">The value of the Proportion property.</param>
+    public static void SetProportion(AvaloniaObject control, double value)
+    {
+        control.SetValue(ProportionProperty, value);
+    }
+
+    /// <summary>
+    /// Defines the IsEmpty attached property.
+    /// </summary>
+    public static readonly AttachedProperty<bool> IsEmptyProperty =
+        AvaloniaProperty.RegisterAttached<ProportionalStackPanel, Control, bool>("IsEmpty", false, false, BindingMode.TwoWay);
+
+    /// <summary>
+    /// Gets the value of the IsEmpty attached property on the specified control.
+    /// </summary>
+    /// <param name="control">The control.</param>
+    /// <returns>The IsEmpty attached property.</returns>
+    public static bool GetIsEmpty(AvaloniaObject control)
+    {
+        return control.GetValue(IsEmptyProperty);
+    }
+
+    /// <summary>
+    /// Sets the value of the IsEmpty attached property on the specified control.
+    /// </summary>
+    /// <param name="control">The control.</param>
+    /// <param name="value">The value of the IsEmpty property.</param>
+    public static void SetIsEmpty(AvaloniaObject control, bool value)
+    {
+        control.SetValue(IsEmptyProperty, value);
+    }
+
     private void AssignProportions(global::Avalonia.Controls.Controls children)
     {
         var assignedProportion = 0.0;
@@ -36,12 +89,12 @@ private void AssignProportions(global::Avalonia.Controls.Controls children)
         for (var i = 0; i < children.Count; i++)
         {
             var control = children[i];
-            var isEmpty = ProportionalStackPanelSplitter.GetControlIsEmpty(control);
+            var isEmpty = GetIsEmpty(control);
             var isSplitter = ProportionalStackPanelSplitter.IsSplitter(control, out _);
 
             if (!isSplitter)
             {
-                var proportion = ProportionalStackPanelSplitter.GetControlProportion(control);
+                var proportion = GetProportion(control);
 
                 if (isEmpty)
                 {
@@ -64,14 +117,14 @@ private void AssignProportions(global::Avalonia.Controls.Controls children)
             var toAssign = assignedProportion;
             foreach (var control in children.Where(c =>
                      {
-                         var isEmpty = ProportionalStackPanelSplitter.GetControlIsEmpty(c);
-                         return !isEmpty && double.IsNaN(ProportionalStackPanelSplitter.GetControlProportion(c));
+                         var isEmpty = GetIsEmpty(c);
+                         return !isEmpty && double.IsNaN(GetProportion(c));
                      }))
             {
                 if (!ProportionalStackPanelSplitter.IsSplitter(control, out _))
                 {
                     var proportion = (1.0 - toAssign) / unassignedProportions;
-                    ProportionalStackPanelSplitter.SetControlProportion(control, proportion);
+                    SetProportion(control, proportion);
                     assignedProportion += (1.0 - toAssign) / unassignedProportions;
                 }
             }
@@ -85,12 +138,12 @@ private void AssignProportions(global::Avalonia.Controls.Controls children)
 
             foreach (var child in children.Where(c =>
                      {
-                         var isEmpty = ProportionalStackPanelSplitter.GetControlIsEmpty(c);
+                         var isEmpty = GetIsEmpty(c);
                          return !isEmpty && !ProportionalStackPanelSplitter.IsSplitter(c, out _);
                      }))
             {
-                var proportion = ProportionalStackPanelSplitter.GetControlProportion(child) + toAdd;
-                ProportionalStackPanelSplitter.SetControlProportion(child, proportion);
+                var proportion = GetProportion(child) + toAdd;
+                SetProportion(child, proportion);
             }
         }
         else if (assignedProportion > 1)
@@ -101,12 +154,12 @@ private void AssignProportions(global::Avalonia.Controls.Controls children)
 
             foreach (var child in children.Where(c =>
                      {
-                         var isEmpty = ProportionalStackPanelSplitter.GetControlIsEmpty(c);
+                         var isEmpty = GetIsEmpty(c);
                          return !isEmpty && !ProportionalStackPanelSplitter.IsSplitter(c, out _);
                      }))
             {
-                var proportion = ProportionalStackPanelSplitter.GetControlProportion(child) - toRemove;
-                ProportionalStackPanelSplitter.SetControlProportion(child, proportion);
+                var proportion = GetProportion(child) - toRemove;
+                SetProportion(child, proportion);
             }
         }
     }
@@ -132,7 +185,7 @@ private double GetTotalSplitterThickness(global::Avalonia.Controls.Controls chil
                 if (i + 1 < Children.Count)
                 {
                     var nextControl = Children[i + 1];
-                    var nextIsEmpty = ProportionalStackPanelSplitter.GetControlIsEmpty(nextControl);
+                    var nextIsEmpty = GetIsEmpty(nextControl);
                     if (nextIsEmpty)
                     {
                         continue;
@@ -144,7 +197,7 @@ private double GetTotalSplitterThickness(global::Avalonia.Controls.Controls chil
             }
             else
             {
-                previousIsEmpty = ProportionalStackPanelSplitter.GetControlIsEmpty(c);
+                previousIsEmpty = GetIsEmpty(c);
             }
         }
 
@@ -184,9 +237,9 @@ protected override Size MeasureOverride(Size constraint)
                 Math.Max(0.0, constraint.Width - usedWidth - splitterThickness),
                 Math.Max(0.0, constraint.Height - usedHeight - splitterThickness));
 
-            var proportion = ProportionalStackPanelSplitter.GetControlProportion(control);
+            var proportion = GetProportion(control);
 
-            var isEmpty = ProportionalStackPanelSplitter.GetControlIsEmpty(control);
+            var isEmpty = !isSplitter && GetIsEmpty(control);
             if (isEmpty)
             {
                 // TODO: Also handle next is empty.
@@ -224,7 +277,7 @@ protected override Size MeasureOverride(Size constraint)
                 if (i + 1 < Children.Count)
                 {
                     var nextControl = Children[i + 1];
-                    nextIsEmpty = ProportionalStackPanelSplitter.GetControlIsEmpty(nextControl);
+                    nextIsEmpty = !ProportionalStackPanelSplitter.IsSplitter(nextControl, out _ ) && GetIsEmpty(nextControl);
                 }
 
                 if (previousIsEmpty || nextIsEmpty)
@@ -304,7 +357,9 @@ protected override Size ArrangeOverride(Size arrangeSize)
         {
             var control = Children[i];
 
-            var isEmpty = ProportionalStackPanelSplitter.GetControlIsEmpty(control);
+            var isSplitter = ProportionalStackPanelSplitter.IsSplitter(control, out _);
+
+            var isEmpty = !isSplitter && GetIsEmpty(control);
             if (isEmpty)
             {
                 // TODO: Also handle next is empty.
@@ -315,13 +370,11 @@ protected override Size ArrangeOverride(Size arrangeSize)
                 continue;
             }
 
-            var isSplitter = ProportionalStackPanelSplitter.IsSplitter(control, out _);
-            
             var nextIsEmpty = false;
             if (i + 1 < Children.Count)
             {
                 var nextControl = Children[i + 1];
-                nextIsEmpty = ProportionalStackPanelSplitter.GetControlIsEmpty(nextControl);
+                nextIsEmpty = !ProportionalStackPanelSplitter.IsSplitter(nextControl, out _) && GetIsEmpty(nextControl);
             }
 
             if (isSplitter && (previousIsEmpty || nextIsEmpty))
@@ -347,7 +400,7 @@ protected override Size ArrangeOverride(Size arrangeSize)
             if (index < Children.Count)
             {
                 var desiredSize = control.DesiredSize;
-                var proportion = ProportionalStackPanelSplitter.GetControlProportion(control);
+                var proportion = GetProportion(control);
 
                 switch (Orientation)
                 {
@@ -405,4 +458,12 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
             InvalidateMeasure();
         }
     }
+
+    static ProportionalStackPanel()
+    {
+        AffectsParentMeasure<ProportionalStackPanel>(IsEmptyProperty);
+        AffectsParentArrange<ProportionalStackPanel>(IsEmptyProperty);
+        AffectsParentMeasure<ProportionalStackPanel>(ProportionProperty);
+        AffectsParentArrange<ProportionalStackPanel>(ProportionProperty);
+    }
 }
diff --git a/src/Dock.Avalonia/Controls/ProportionalStackPanelSplitter.axaml.cs b/src/Dock.Avalonia/Controls/ProportionalStackPanelSplitter.axaml.cs
index a318b46a0..19f4e4a69 100644
--- a/src/Dock.Avalonia/Controls/ProportionalStackPanelSplitter.axaml.cs
+++ b/src/Dock.Avalonia/Controls/ProportionalStackPanelSplitter.axaml.cs
@@ -1,4 +1,5 @@
-using Avalonia;
+using System;
+using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Presenters;
@@ -16,58 +17,6 @@ namespace Dock.Avalonia.Controls;
 [PseudoClasses(":horizontal", ":vertical")]
 public class ProportionalStackPanelSplitter : Thumb
 {
-    /// <summary>
-    /// Defines the Proportion attached property.
-    /// </summary>
-    public static readonly AttachedProperty<double> ProportionProperty =
-        AvaloniaProperty.RegisterAttached<ProportionalStackPanelSplitter, Control, double>("Proportion", double.NaN, false, BindingMode.TwoWay);
-
-    /// <summary>
-    /// Gets the value of the Proportion attached property on the specified control.
-    /// </summary>
-    /// <param name="control">The control.</param>
-    /// <returns>The Proportion attached property.</returns>
-    public static double GetProportion(AvaloniaObject control)
-    {
-        return control.GetValue(ProportionProperty);
-    }
-
-    /// <summary>
-    /// Sets the value of the Proportion attached property on the specified control.
-    /// </summary>
-    /// <param name="control">The control.</param>
-    /// <param name="value">The value of the Proportion property.</param>
-    public static void SetProportion(AvaloniaObject control, double value)
-    {
-        control.SetValue(ProportionProperty, value);
-    }
-
-    /// <summary>
-    /// Defines the IsEmpty attached property.
-    /// </summary>
-    public static readonly AttachedProperty<bool> IsEmptyProperty =
-        AvaloniaProperty.RegisterAttached<ProportionalStackPanelSplitter, Control, bool>("IsEmpty", false, false, BindingMode.TwoWay);
-
-    /// <summary>
-    /// Gets the value of the IsEmpty attached property on the specified control.
-    /// </summary>
-    /// <param name="control">The control.</param>
-    /// <returns>The IsEmpty attached property.</returns>
-    public static bool GetIsEmpty(AvaloniaObject control)
-    {
-        return control.GetValue(IsEmptyProperty);
-    }
-
-    /// <summary>
-    /// Sets the value of the IsEmpty attached property on the specified control.
-    /// </summary>
-    /// <param name="control">The control.</param>
-    /// <param name="value">The value of the IsEmpty property.</param>
-    public static void SetIsEmpty(AvaloniaObject control, bool value)
-    {
-        control.SetValue(IsEmptyProperty, value);
-    }
-
     /// <summary>
     /// Defines the <see cref="Thickness"/> property.
     /// </summary>
@@ -139,79 +88,6 @@ internal static bool IsSplitter(Control? control, out ProportionalStackPanelSpli
         return false;
     }
 
-    internal static void SetControlProportion(Control? control, double proportion)
-    {
-        if (control is ContentPresenter contentPresenter)
-        {
-            if (contentPresenter.Child is null)
-            {
-                contentPresenter.UpdateChild();
-            }
-
-            if (contentPresenter.Child is not null)
-            {
-                SetProportion(contentPresenter.Child, proportion);
-            }
-        }
-        else
-        {
-            if (control is not null)
-            {
-                SetProportion(control, proportion);
-            }
-        }
-    }
-
-    internal static double GetControlProportion(Control? control)
-    {
-        if (control is ContentPresenter contentPresenter)
-        {
-            if (contentPresenter.Child is null)
-            {
-                contentPresenter.UpdateChild();
-            }
-
-            if (contentPresenter.Child is not null)
-            {
-                return GetProportion(contentPresenter.Child);
-            }
-
-            return double.NaN;
-        }
-
-        if (control is not null)
-        {
-            return GetProportion(control);
-        }
-
-        return double.NaN;
-    }
-
-    internal static bool GetControlIsEmpty(Control? control)
-    {
-        if (control is ContentPresenter contentPresenter)
-        {
-            if (contentPresenter.Child is null)
-            {
-                contentPresenter.UpdateChild();
-            }
-
-            if (contentPresenter.Child is not null)
-            {
-                return GetIsEmpty(contentPresenter.Child);
-            }
-
-            return false;
-        }
-
-        if (control is not null)
-        {
-            return GetIsEmpty(control);
-        }
-
-        return false;
-    }
-
     /// <inheritdoc/>
     protected override void OnPointerPressed(PointerPressedEventArgs e)
     {
@@ -304,18 +180,7 @@ protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
             nextIndex = children.IndexOf(this) + 1;
         }
 
-        var child = children[nextIndex];
-        if (child is ContentPresenter contentPresenter)
-        {
-            if (contentPresenter.Child is null)
-            {
-                contentPresenter.UpdateChild();
-            }
-
-            return contentPresenter.Child;
-        }
-
-        return child;
+        return children[nextIndex];
     }
 
     private void SetTargetProportion(double dragDelta)
@@ -329,8 +194,8 @@ private void SetTargetProportion(double dragDelta)
 
         var child = FindNextChild(panel);
 
-        var targetElementProportion = GetControlProportion(target);
-        var neighbourProportion = child is not null ? GetControlProportion(child) : double.NaN;
+        var targetElementProportion = ProportionalStackPanel.GetProportion(target);
+        var neighbourProportion = child is not null ? ProportionalStackPanel.GetProportion(child) : double.NaN;
 
         var dProportion = dragDelta / (panel.Orientation == Orientation.Vertical ? panel.Bounds.Height : panel.Bounds.Width);
 
@@ -363,15 +228,12 @@ private void SetTargetProportion(double dragDelta)
             targetElementProportion += dProportion;
         }
 
-        SetProportion(target, targetElementProportion);
+        ProportionalStackPanel.SetProportion(target, targetElementProportion);
 
         if (child is not null)
         {
-            SetProportion(child, neighbourProportion);
+            ProportionalStackPanel.SetProportion(child, neighbourProportion);
         }
-
-        panel.InvalidateMeasure();
-        panel.InvalidateArrange();
     }
 
     private void UpdateHeightOrWidth()
@@ -422,17 +284,10 @@ private void UpdateHeightOrWidth()
             }
 
             var parent = Parent as Control;
-            var index = parent is null ? -1 :panel.Children.IndexOf(parent);
+            var index = parent is null ? -1 : panel.Children.IndexOf(parent);
             if (index > 0 && panel.Children.Count > 0)
             {
-                if (panel.Children[index - 1] is ContentPresenter contentPresenter)
-                {
-                    return contentPresenter.Child;
-                }
-                else
-                {
-                    return null;
-                }
+                return panel.Children[index - 1];
             }
         }
         else
diff --git a/src/Dock.Avalonia/Controls/ToolDockControl.axaml b/src/Dock.Avalonia/Controls/ToolDockControl.axaml
index 4ad5ee920..0c401fb7d 100644
--- a/src/Dock.Avalonia/Controls/ToolDockControl.axaml
+++ b/src/Dock.Avalonia/Controls/ToolDockControl.axaml
@@ -7,14 +7,10 @@
 
   <ControlTheme x:Key="{x:Type ToolDockControl}" TargetType="ToolDockControl">
 
-    <Setter Property="(ProportionalStackPanelSplitter.Proportion)" Value="{Binding Proportion}" x:DataType="core:IDock" />
-    <Setter Property="(ProportionalStackPanelSplitter.IsEmpty)" Value="{Binding IsEmpty}" x:DataType="core:IDock" />
-
     <Setter Property="Template">
       <ControlTemplate>
         <DockableControl Name="PART_DockableControl"
-                         TrackingMode="Visible" 
-                         ProportionalStackPanelSplitter.Proportion="{Binding Proportion}"
+                         TrackingMode="Visible"
                          x:DataType="core:IDock">
           <ToolChromeControl IsActive="{Binding IsActive}"
                              IsVisible="{Binding !!VisibleDockables.Count}"
diff --git a/src/Dock.Avalonia/Controls/ToolDockControl.axaml.cs b/src/Dock.Avalonia/Controls/ToolDockControl.axaml.cs
index 50252c2f1..bcd3d7a1f 100644
--- a/src/Dock.Avalonia/Controls/ToolDockControl.axaml.cs
+++ b/src/Dock.Avalonia/Controls/ToolDockControl.axaml.cs
@@ -26,29 +26,4 @@ public class ToolDockControl : TemplatedControl
 
         return null;
     }
-
-    /// <inheritdoc/>
-    protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
-    {
-        base.OnPropertyChanged(change);
-
-        if (change.Property == ProportionalStackPanelSplitter.IsEmptyProperty)
-        {
-            // TODO: Handle invalidation better.
-            if (GetPanel() is { } panel)
-            {
-                panel.InvalidateMeasure();
-                panel.InvalidateArrange();
-                panel.UpdateLayout();
-
-                panel.InvalidateMeasure();
-                panel.InvalidateArrange();
-                panel.UpdateLayout();
-
-                panel.InvalidateMeasure();
-                panel.InvalidateArrange();
-                panel.UpdateLayout();
-            }
-        }
-    }
 }
diff --git a/src/Dock.Model.Avalonia/Controls/ProportionalDockSplitter.cs b/src/Dock.Model.Avalonia/Controls/ProportionalDockSplitter.cs
index 5182849b9..84259b640 100644
--- a/src/Dock.Model.Avalonia/Controls/ProportionalDockSplitter.cs
+++ b/src/Dock.Model.Avalonia/Controls/ProportionalDockSplitter.cs
@@ -1,4 +1,6 @@
-using System.Runtime.Serialization;
+using System;
+using System.Runtime.Serialization;
+using Avalonia;
 using Dock.Model.Avalonia.Core;
 using Dock.Model.Controls;
 
diff --git a/tests/Dock.Avalonia.UnitTests/Controls/ProportionalStackPanelTests.cs b/tests/Dock.Avalonia.UnitTests/Controls/ProportionalStackPanelTests.cs
index 807c08ae9..263f5f880 100644
--- a/tests/Dock.Avalonia.UnitTests/Controls/ProportionalStackPanelTests.cs
+++ b/tests/Dock.Avalonia.UnitTests/Controls/ProportionalStackPanelTests.cs
@@ -85,7 +85,7 @@ public void Lays_Out_Children_Default()
                         new Border()
                         {
                             Background = Brushes.Red,
-                            [ProportionalStackPanelSplitter.ProportionProperty] = 0.5
+                            [ProportionalStackPanel.ProportionProperty] = 0.5
                         },
                         new ProportionalStackPanelSplitter(),
                         new Border()
@@ -138,7 +138,7 @@ public void Lays_Out_Children_Default()
                         new Border()
                         {
                             Background=Brushes.Red,
-                            [ProportionalStackPanelSplitter.ProportionProperty] = 0.5
+                            [ProportionalStackPanel.ProportionProperty] = 0.5
                         }
                     }
                 },