diff --git a/src/Avalonia.Controls/Viewbox.cs b/src/Avalonia.Controls/Viewbox.cs
index 79e9684c67..50b9560cac 100644
--- a/src/Avalonia.Controls/Viewbox.cs
+++ b/src/Avalonia.Controls/Viewbox.cs
@@ -76,7 +76,7 @@ namespace Avalonia.Controls
         /// Gets or sets the transform applied to the container visual that
         /// hosts the child of the Viewbox
         /// </summary>
-        protected ITransform? InternalTransform
+        protected internal ITransform? InternalTransform
         {
             get => _containerVisual.RenderTransform;
             set => _containerVisual.RenderTransform = value;
diff --git a/tests/Avalonia.Controls.UnitTests/ViewboxTests.cs b/tests/Avalonia.Controls.UnitTests/ViewboxTests.cs
index 7eaec35506..d33e55341b 100644
--- a/tests/Avalonia.Controls.UnitTests/ViewboxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ViewboxTests.cs
@@ -18,7 +18,7 @@ namespace Avalonia.Controls.UnitTests
             target.Arrange(new Rect(new Point(0, 0), target.DesiredSize));
 
             Assert.Equal(new Size(200, 100), target.DesiredSize);
-            var scaleTransform = target.Child.RenderTransform as ScaleTransform;
+            var scaleTransform = target.InternalTransform as ScaleTransform;
 
             Assert.NotNull(scaleTransform);
             Assert.Equal(2.0, scaleTransform.ScaleX);
@@ -36,7 +36,7 @@ namespace Avalonia.Controls.UnitTests
             target.Arrange(new Rect(new Point(0, 0), target.DesiredSize));
 
             Assert.Equal(new Size(100, 50), target.DesiredSize);
-            var scaleTransform = target.Child.RenderTransform as ScaleTransform;
+            var scaleTransform = target.InternalTransform as ScaleTransform;
 
             Assert.NotNull(scaleTransform);
             Assert.Equal(1.0, scaleTransform.ScaleX);
@@ -54,7 +54,7 @@ namespace Avalonia.Controls.UnitTests
             target.Arrange(new Rect(new Point(0, 0), target.DesiredSize));
 
             Assert.Equal(new Size(200, 200), target.DesiredSize);
-            var scaleTransform = target.Child.RenderTransform as ScaleTransform;
+            var scaleTransform = target.InternalTransform as ScaleTransform;
 
             Assert.NotNull(scaleTransform);
             Assert.Equal(2.0, scaleTransform.ScaleX);
@@ -72,7 +72,7 @@ namespace Avalonia.Controls.UnitTests
             target.Arrange(new Rect(new Point(0, 0), target.DesiredSize));
 
             Assert.Equal(new Size(200, 200), target.DesiredSize);
-            var scaleTransform = target.Child.RenderTransform as ScaleTransform;
+            var scaleTransform = target.InternalTransform as ScaleTransform;
 
             Assert.NotNull(scaleTransform);
             Assert.Equal(4.0, scaleTransform.ScaleX);
@@ -90,7 +90,7 @@ namespace Avalonia.Controls.UnitTests
             target.Arrange(new Rect(new Point(0, 0), target.DesiredSize));
 
             Assert.Equal(new Size(400, 200), target.DesiredSize);
-            var scaleTransform = target.Child.RenderTransform as ScaleTransform;
+            var scaleTransform = target.InternalTransform as ScaleTransform;
 
             Assert.NotNull(scaleTransform);
             Assert.Equal(4.0, scaleTransform.ScaleX);
@@ -108,7 +108,7 @@ namespace Avalonia.Controls.UnitTests
             target.Arrange(new Rect(new Point(0, 0), target.DesiredSize));
 
             Assert.Equal(new Size(200, 100), target.DesiredSize);
-            var scaleTransform = target.Child.RenderTransform as ScaleTransform;
+            var scaleTransform = target.InternalTransform as ScaleTransform;
 
             Assert.NotNull(scaleTransform);
             Assert.Equal(2.0, scaleTransform.ScaleX);
@@ -136,7 +136,7 @@ namespace Avalonia.Controls.UnitTests
 
             Assert.Equal(new Size(expectedWidth, expectedHeight), target.DesiredSize);
 
-            var scaleTransform = target.Child.RenderTransform as ScaleTransform;
+            var scaleTransform = target.InternalTransform as ScaleTransform;
 
             Assert.NotNull(scaleTransform);
             Assert.Equal(expectedScale, scaleTransform.ScaleX);
@@ -164,7 +164,7 @@ namespace Avalonia.Controls.UnitTests
 
             Assert.Equal(new Size(expectedWidth, expectedHeight), target.DesiredSize);
 
-            var scaleTransform = target.Child.RenderTransform as ScaleTransform;
+            var scaleTransform = target.InternalTransform as ScaleTransform;
 
             Assert.NotNull(scaleTransform);
             Assert.Equal(expectedScale, scaleTransform.ScaleX);