diff --git a/Source/OpenTK/Graphics/ES20/Helper.cs b/Source/OpenTK/Graphics/ES20/Helper.cs
index fe989cfc..1ba792d9 100644
--- a/Source/OpenTK/Graphics/ES20/Helper.cs
+++ b/Source/OpenTK/Graphics/ES20/Helper.cs
@@ -389,7 +389,7 @@ namespace OpenTK.Graphics.ES20
         {
             GL.Viewport(rectangle.X, rectangle.Y, rectangle.Width, rectangle.Height);
         }
-
+#if NO_SYSDRAWING
         public static void Viewport(OpenTK.Point location, OpenTK.Size size)
         {
             GL.Viewport(location.X, location.Y, size.Width, size.Height);
@@ -399,7 +399,7 @@ namespace OpenTK.Graphics.ES20
         {
             GL.Viewport(rectangle.X, rectangle.Y, rectangle.Width, rectangle.Height);
         }
-
+#endif
         #endregion
 
 #pragma warning restore 3019
diff --git a/Source/OpenTK/Graphics/OpenGL/GLHelper.cs b/Source/OpenTK/Graphics/OpenGL/GLHelper.cs
index fe6eb1ac..49390879 100644
--- a/Source/OpenTK/Graphics/OpenGL/GLHelper.cs
+++ b/Source/OpenTK/Graphics/OpenGL/GLHelper.cs
@@ -826,7 +826,7 @@ namespace OpenTK.Graphics.OpenGL
         {
             GL.Viewport(rectangle.X, rectangle.Y, rectangle.Width, rectangle.Height);
         }
-
+#if NO_SYSDRAWING
         public static void Viewport(OpenTK.Point location, OpenTK.Size size)
         {
             GL.Viewport(location.X, location.Y, size.Width, size.Height);
@@ -836,7 +836,7 @@ namespace OpenTK.Graphics.OpenGL
         {
             GL.Viewport(rectangle.X, rectangle.Y, rectangle.Width, rectangle.Height);
         }
-
+#endif
         #endregion
 
         #region TexEnv
diff --git a/Source/OpenTK/Math/Point.cs b/Source/OpenTK/Math/Point.cs
index 52e387ba..e54bb090 100644
--- a/Source/OpenTK/Math/Point.cs
+++ b/Source/OpenTK/Math/Point.cs
@@ -31,6 +31,7 @@ using System.Text;
 
 namespace OpenTK
 {
+#if NO_SYSDRAWING
     /// <summary>
     /// Defines a point on a two-dimensional plane.
     /// </summary>
@@ -230,4 +231,5 @@ namespace OpenTK
 
         #endregion
     }
+#endif
 }
diff --git a/Source/OpenTK/Math/Rectangle.cs b/Source/OpenTK/Math/Rectangle.cs
index a433712a..700dbbf4 100644
--- a/Source/OpenTK/Math/Rectangle.cs
+++ b/Source/OpenTK/Math/Rectangle.cs
@@ -31,6 +31,7 @@ using System.Text;
 
 namespace OpenTK
 {
+#if NO_SYSDRAWING
     /// <summary>
     /// Represents a rectangular region on a two-dimensional plane.
     /// </summary>
@@ -318,4 +319,5 @@ namespace OpenTK
 
         #endregion
     }
+#endif
 }
diff --git a/Source/OpenTK/Math/Size.cs b/Source/OpenTK/Math/Size.cs
index 0459a03f..04e556a8 100644
--- a/Source/OpenTK/Math/Size.cs
+++ b/Source/OpenTK/Math/Size.cs
@@ -31,6 +31,7 @@ using System.Text;
 
 namespace OpenTK
 {
+#if NO_SYSDRAWING
     /// <summary>
     /// Stores the width and height of a rectangle.
     /// </summary>
@@ -217,4 +218,5 @@ namespace OpenTK
         
         #endregion
     }
+#endif
 }
diff --git a/Source/OpenTK/Platform/MacOS/QuartzDisplayDeviceDriver.cs b/Source/OpenTK/Platform/MacOS/QuartzDisplayDeviceDriver.cs
index 3f1c8ea2..dc9f4ac9 100644
--- a/Source/OpenTK/Platform/MacOS/QuartzDisplayDeviceDriver.cs
+++ b/Source/OpenTK/Platform/MacOS/QuartzDisplayDeviceDriver.cs
@@ -1,11 +1,10 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Text;
 
 namespace OpenTK.Platform.MacOS
 {
-    using Graphics;
+    using System.Drawing;
     using Carbon;
 
     class QuartzDisplayDeviceDriver : IDisplayDeviceDriver
diff --git a/Source/OpenTK/Platform/X11/X11XrandrDisplayDevice.cs b/Source/OpenTK/Platform/X11/X11XrandrDisplayDevice.cs
index b6e4ec2f..f52cc7d8 100644
--- a/Source/OpenTK/Platform/X11/X11XrandrDisplayDevice.cs
+++ b/Source/OpenTK/Platform/X11/X11XrandrDisplayDevice.cs
@@ -8,11 +8,9 @@
 
 using System;
 using System.Collections.Generic;
-using System.Runtime.InteropServices;
-using System.Text;
-
-using OpenTK.Graphics;
 using System.Diagnostics;
+using System.Drawing;
+using System.Runtime.InteropServices;
 
 namespace OpenTK.Platform.X11
 {