diff --git a/Source/OpenTK/Audio/OpenAL/Alut/Alut.cs b/Source/OpenTK/Audio/OpenAL/Alut/Alut.cs
index a71a6aaa..c37848d5 100644
--- a/Source/OpenTK/Audio/OpenAL/Alut/Alut.cs
+++ b/Source/OpenTK/Audio/OpenAL/Alut/Alut.cs
@@ -15,6 +15,7 @@ namespace OpenTK.Audio
 {
 
     /// <summary>Alut, FreeAlut = Free Audio Library Utilities</summary>
+    [Obsolete("Use OpenTK.Audio.AudioContext and OpenTK.Audio.Alc instead.")]
     public static class Alut
     {
         #region Constants
diff --git a/Source/OpenTK/Graphics/Glu/GluHelper.cs b/Source/OpenTK/Graphics/Glu/GluHelper.cs
index 2644a315..87b632ff 100644
--- a/Source/OpenTK/Graphics/Glu/GluHelper.cs
+++ b/Source/OpenTK/Graphics/Glu/GluHelper.cs
@@ -17,6 +17,7 @@ using OpenTK.Math;
 
 namespace OpenTK.Graphics
 {
+    [Obsolete("Use OpenTK math functions instead.")]
     public static partial class Glu
     {
         private const string Library = "glu32.dll";