diff --git a/src/Dock.Avalonia/Controls/ProportionalStackPanel.cs b/src/Dock.Avalonia/Controls/ProportionalStackPanel.cs
index f937bcb27..dd8df8743 100644
--- a/src/Dock.Avalonia/Controls/ProportionalStackPanel.cs
+++ b/src/Dock.Avalonia/Controls/ProportionalStackPanel.cs
@@ -224,7 +224,7 @@ protected override Size MeasureOverride(Size constraint)
 
         AssignProportions(Children);
 
-        var previousisCollapsed = false;
+        var needsNextSplitter = false;
         
         // Measure each of the Children
         for (var i = 0; i < Children.Count; i++)
@@ -242,8 +242,6 @@ protected override Size MeasureOverride(Size constraint)
             var isCollapsed = !isSplitter && GetIsCollapsed(control);
             if (isCollapsed)
             {
-                // TODO: Also handle next is empty.
-                previousisCollapsed = true;
                 var size = new Size();
                 control.Measure(size);
                 continue;
@@ -270,29 +268,22 @@ protected override Size MeasureOverride(Size constraint)
                         break;
                     }
                 }
+
+                needsNextSplitter = true;
             }
             else
             {
-                var nextisCollapsed = false;
-                if (i + 1 < Children.Count)
-                {
-                    var nextControl = Children[i + 1];
-                    nextisCollapsed = !ProportionalStackPanelSplitter.IsSplitter(nextControl, out _ ) && GetIsCollapsed(nextControl);
-                }
-
-                if (previousisCollapsed || nextisCollapsed)
+                if (!needsNextSplitter)
                 {
                     var size = new Size();
                     control.Measure(size);
-                    previousisCollapsed = true;
                     continue;
                 }
 
                 control.Measure(remainingSize);
+                needsNextSplitter = false;
             }
 
-            previousisCollapsed = false;
-
             var desiredSize = control.DesiredSize;
 
             // Decrease the remaining space for the rest of the children
@@ -351,7 +342,7 @@ protected override Size ArrangeOverride(Size arrangeSize)
 
         AssignProportions(Children);
 
-        var previousisCollapsed = false;
+        var needsNextSplitter = false;
 
         for (var i = 0; i < Children.Count; i++)
         {
@@ -362,31 +353,23 @@ protected override Size ArrangeOverride(Size arrangeSize)
             var isCollapsed = !isSplitter && GetIsCollapsed(control);
             if (isCollapsed)
             {
-                // TODO: Also handle next is empty.
-                previousisCollapsed = true;
                 var rect = new Rect();
                 control.Arrange(rect);
                 index++;
                 continue;
             }
 
-            var nextisCollapsed = false;
-            if (i + 1 < Children.Count)
-            {
-                var nextControl = Children[i + 1];
-                nextisCollapsed = !ProportionalStackPanelSplitter.IsSplitter(nextControl, out _) && GetIsCollapsed(nextControl);
-            }
-
-            if (isSplitter && (previousisCollapsed || nextisCollapsed))
+            if (!isSplitter)
+                needsNextSplitter = true;
+            else if (isSplitter && !needsNextSplitter)
             {
                 var rect = new Rect();
                 control.Arrange(rect);
                 index++;
+                needsNextSplitter = false;
                 continue;
             }
 
-            previousisCollapsed = false;
-
             // Determine the remaining space left to arrange the element
             var remainingRect = new Rect(
                 left,
diff --git a/src/Dock.Avalonia/Controls/ProportionalStackPanelSplitter.axaml.cs b/src/Dock.Avalonia/Controls/ProportionalStackPanelSplitter.axaml.cs
index 19f4e4a69..76077745f 100644
--- a/src/Dock.Avalonia/Controls/ProportionalStackPanelSplitter.axaml.cs
+++ b/src/Dock.Avalonia/Controls/ProportionalStackPanelSplitter.axaml.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics;
 using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Controls.Metadata;
@@ -168,26 +169,19 @@ protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
 
     private Control? FindNextChild(ProportionalStackPanel panel)
     {
-        var children = panel.Children;
-        int nextIndex;
-
-        if (Parent is ContentPresenter parentContentPresenter)
-        {
-            nextIndex = children.IndexOf(parentContentPresenter) + 1;
-        }
-        else
-        {
-            nextIndex = children.IndexOf(this) + 1;
-        }
-
-        return children[nextIndex];
+        return GetSiblingInDirection(panel, 1);
     }
 
     private void SetTargetProportion(double dragDelta)
     {
-        var target = GetTargetElement();
         var panel = GetPanel();
-        if (target is null || panel is null)
+        if (panel == null)
+        {
+            return;
+        }
+        
+        var target = GetTargetElement(panel);
+        if (target is null)
         {
             return;
         }
@@ -274,35 +268,33 @@ private void UpdateHeightOrWidth()
         return null;
     }
 
-    private Control? GetTargetElement()
+    private Control? GetSiblingInDirection(ProportionalStackPanel panel, int direction)
     {
-        if (Parent is ContentPresenter presenter)
-        {
-            if (presenter.GetVisualParent() is not Panel panel)
-            {
-                return null;
-            }
+        Debug.Assert(direction == -1 || direction == 1);
+        
+        var children = panel.Children;
+        int siblingIndex;
 
-            var parent = Parent as Control;
-            var index = parent is null ? -1 : panel.Children.IndexOf(parent);
-            if (index > 0 && panel.Children.Count > 0)
-            {
-                return panel.Children[index - 1];
-            }
+        if (Parent is ContentPresenter parentContentPresenter)
+        {
+            siblingIndex = children.IndexOf(parentContentPresenter) + direction;
         }
         else
         {
-            var panel = GetPanel();
-            if (panel is not null)
-            {
-                var index = panel.Children.IndexOf(this);
-                if (index > 0 && panel.Children.Count > 0)
-                {
-                    return panel.Children[index - 1];
-                }
-            }
+            siblingIndex = children.IndexOf(this) + direction;
         }
 
-        return null;
+        while (siblingIndex >= 0 && siblingIndex < children.Count && 
+               (ProportionalStackPanel.GetIsCollapsed(children[siblingIndex]) || IsSplitter(children[siblingIndex], out _)))
+        {
+            siblingIndex += direction;
+        }
+
+        return siblingIndex >= 0 && siblingIndex < children.Count ? children[siblingIndex] : null;
+    }
+    
+    private Control? GetTargetElement(ProportionalStackPanel panel)
+    {
+        return GetSiblingInDirection(panel, -1);
     }
 }