diff --git a/Source/OpenTK/OpenTK.csproj b/Source/OpenTK/OpenTK.csproj
index 0582de96..8c3931fc 100644
--- a/Source/OpenTK/OpenTK.csproj
+++ b/Source/OpenTK/OpenTK.csproj
@@ -166,6 +166,7 @@
     <Compile Include="Platform\MappedGamePadDriver.cs" />
     <Compile Include="Platform\Windows\WinInputBase.cs" />
     <Compile Include="Platform\Windows\XInputJoystick.cs" />
+    <Compile Include="Platform\X11\Bindings\INotify.cs" />
     <Compile Include="ToolkitOptions.cs" />
     <Compile Include="WindowBorder.cs">
       <SubType>Code</SubType>