diff --git a/sample/sample.csproj b/sample/sample.csproj
index dd7948446..a7450e77b 100644
--- a/sample/sample.csproj
+++ b/sample/sample.csproj
@@ -105,6 +105,9 @@
     <Compile Include="test\WidgetViewer.cs" />
     <Compile Include="CustomScrollableWidget.cs" />
     <Compile Include="AsyncSample.cs" />
+    <Compile Include="gio\AppInfo.cs" />
+    <Compile Include="gio\Volume.cs" />
+    <Compile Include="gtk-gio\MountOperation.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
   <ItemGroup>