diff --git a/samples/Sandbox/Sandbox.csproj b/samples/Sandbox/Sandbox.csproj
index 7a57a13529..fac565b55a 100644
--- a/samples/Sandbox/Sandbox.csproj
+++ b/samples/Sandbox/Sandbox.csproj
@@ -14,6 +14,7 @@
     <ProjectReference Include="..\..\src\Avalonia.Controls.DataGrid\Avalonia.Controls.DataGrid.csproj" />
     <ProjectReference Include="..\..\src\Avalonia.Fonts.Inter\Avalonia.Fonts.Inter.csproj" />
     <ProjectReference Include="..\..\src\Avalonia.Themes.Fluent\Avalonia.Themes.Fluent.csproj" />
+    <ProjectReference Include="..\..\src\Avalonia.Themes.Simple\Avalonia.Themes.Simple.csproj" />
   </ItemGroup>
   
   <Import Project="..\..\build\SampleApp.props" />