diff --git a/Source/OpenTK/BindingsBase.cs b/Source/OpenTK/BindingsBase.cs
index d1a521dc..4c968a65 100644
--- a/Source/OpenTK/BindingsBase.cs
+++ b/Source/OpenTK/BindingsBase.cs
@@ -111,6 +111,14 @@ namespace OpenTK
         /// </remarks>
         protected abstract IntPtr GetAddress(string funcname);
 
+        /// <summary>
+        /// Gets an object that can be used to synchronize access to the bindings implementation.
+        /// </summary>
+        /// <remarks>This object should be unique across bindings but consistent between bindings
+        /// of the same type. For example, ES10.GL, OpenGL.GL and CL10.CL should all return 
+        /// unique objects, but all instances of ES10.GL should return the same object.</remarks>
+        protected abstract object SyncRoot { get; }
+
         #endregion
 
         #region Internal Members
@@ -141,7 +149,10 @@ namespace OpenTK
                 if (d != null)
                     ++supported;
 
-                f.SetValue(null, d);
+                lock (SyncRoot)
+                {
+                    f.SetValue(null, d);
+                }
             }
 
             rebuildExtensionList = true;
@@ -166,9 +177,12 @@ namespace OpenTK
 
             Delegate old = f.GetValue(null) as Delegate;
             Delegate @new = LoadDelegate(f.Name, f.FieldType);
-            if (old.Target != @new.Target)
+            lock (SyncRoot)
             {
-                f.SetValue(null, @new);
+                if (old.Target != @new.Target)
+                {
+                    f.SetValue(null, @new);
+                }
             }
             return @new != null;
         }
diff --git a/Source/OpenTK/Compute/CL10/CLHelper.cs b/Source/OpenTK/Compute/CL10/CLHelper.cs
index 4c94b65a..22e488fa 100644
--- a/Source/OpenTK/Compute/CL10/CLHelper.cs
+++ b/Source/OpenTK/Compute/CL10/CLHelper.cs
@@ -35,11 +35,12 @@ namespace OpenTK.Compute.CL10
     /// <summary>
     /// Provides access to the OpenCL 1.0 flat API.
     /// </summary>
-    public partial class CL
+    public partial class CL : BindingsBase
     {
-        #region Private Members
+        #region Fields
 
         const string Library = "opencl.dll";
+        static readonly object sync_root = new object();
 
         #endregion
 
@@ -61,5 +62,35 @@ namespace OpenTK.Compute.CL10
         }
 
         #endregion
+
+        #region Protected Members
+
+        /// <summary>
+        /// Returns a synchronization token unique for the GL class.
+        /// </summary>
+        protected override object SyncRoot
+        {
+            get { return sync_root; }
+        }
+
+        /// <summary>
+        /// Not supported yet.
+        /// </summary>
+        /// <param name="funcname">The name of the extension function.</param>
+        /// <returns>A pointer to the extension function, if available; IntPtr.Zero otherwise.</returns>
+        /// <remarks>
+        /// <para>Use <see cref="Marshal.GetDelegateForFunctionPointer"/> to turn this function pointer
+        /// into a callable delegate.</para>
+        /// <para>A non-zero return value does not mean that this extension function is supported. You also
+        /// need to query available extensions through <see cref="GetDeviceInfo"/>.</para>
+        /// <para>This method will always return IntPtr.Zero for core (i.e. non-extension) functions.</para>
+        /// </remarks>
+        protected override IntPtr GetAddress(string funcname)
+        {
+            throw new NotSupportedException();
+            //CL.GetExtensionFunctionAddress
+        }
+
+        #endregion
     }
 }
diff --git a/Source/OpenTK/Graphics/ES10/Helper.cs b/Source/OpenTK/Graphics/ES10/Helper.cs
index da2d4947..16f87c7c 100644
--- a/Source/OpenTK/Graphics/ES10/Helper.cs
+++ b/Source/OpenTK/Graphics/ES10/Helper.cs
@@ -10,5 +10,19 @@ namespace OpenTK.Graphics.ES10
     public sealed partial class GL : GraphicsBindingsBase
     {
         const string Library = "libGLES.dll";
+        static readonly object sync_root = new object();
+
+        #region --- Protected Members ---
+
+        /// <summary>
+        /// Returns a synchronization token unique for the GL class.
+        /// </summary>
+        protected override object SyncRoot
+        {
+            get { return sync_root; }
+        }
+
+        #endregion
+
     }
 }
diff --git a/Source/OpenTK/Graphics/ES11/Helper.cs b/Source/OpenTK/Graphics/ES11/Helper.cs
index eab6d123..49917848 100644
--- a/Source/OpenTK/Graphics/ES11/Helper.cs
+++ b/Source/OpenTK/Graphics/ES11/Helper.cs
@@ -12,5 +12,19 @@ namespace OpenTK.Graphics.ES11
     public sealed partial class GL : GraphicsBindingsBase
     {
         const string Library = "libGLES.dll";
+        static readonly object sync_root = new object();
+
+        #region --- Protected Members ---
+
+        /// <summary>
+        /// Returns a synchronization token unique for the GL class.
+        /// </summary>
+        protected override object SyncRoot
+        {
+            get { return sync_root; }
+        }
+
+        #endregion
+
     }
 }
diff --git a/Source/OpenTK/Graphics/ES20/Helper.cs b/Source/OpenTK/Graphics/ES20/Helper.cs
index 78c9ae4f..4fdd6697 100644
--- a/Source/OpenTK/Graphics/ES20/Helper.cs
+++ b/Source/OpenTK/Graphics/ES20/Helper.cs
@@ -37,6 +37,19 @@ namespace OpenTK.Graphics.ES20
     public sealed partial class GL : GraphicsBindingsBase
     {
         const string Library = "libGLESv2.dll";
+        static readonly object sync_root = new object();
+
+        #region --- Protected Members ---
+
+        /// <summary>
+        /// Returns a synchronization token unique for the GL class.
+        /// </summary>
+        protected override object SyncRoot
+        {
+            get { return sync_root; }
+        }
+
+        #endregion
 
         #region Helper Overloads
 
diff --git a/Source/OpenTK/Graphics/GraphicsBindingsBase.cs b/Source/OpenTK/Graphics/GraphicsBindingsBase.cs
index cf5cd204..8ca5997e 100644
--- a/Source/OpenTK/Graphics/GraphicsBindingsBase.cs
+++ b/Source/OpenTK/Graphics/GraphicsBindingsBase.cs
@@ -32,7 +32,7 @@ namespace OpenTK.Graphics
     /// <summary>
     /// Implements BindingsBase for the OpenTK.Graphics namespace (OpenGL and OpenGL|ES).
     /// </summary>
-    public class GraphicsBindingsBase : BindingsBase
+    public abstract class GraphicsBindingsBase : BindingsBase
     {
         /// <summary>
         /// Retrieves an unmanaged function pointer to the specified function.
diff --git a/Source/OpenTK/Graphics/OpenGL/GLHelper.cs b/Source/OpenTK/Graphics/OpenGL/GLHelper.cs
index fe392a89..af8421b1 100644
--- a/Source/OpenTK/Graphics/OpenGL/GLHelper.cs
+++ b/Source/OpenTK/Graphics/OpenGL/GLHelper.cs
@@ -52,7 +52,8 @@ namespace OpenTK.Graphics.OpenGL
 
         internal const string Library = "opengl32.dll";
 
-        private static SortedList<string, bool> AvailableExtensions = new SortedList<string, bool>();
+        static SortedList<string, bool> AvailableExtensions = new SortedList<string, bool>();
+        static readonly object sync_root = new object();
 
         #endregion
 
@@ -335,6 +336,18 @@ namespace OpenTK.Graphics.OpenGL
 #endif
         #endregion
 
+        #region --- Protected Members ---
+
+        /// <summary>
+        /// Returns a synchronization token unique for the GL class.
+        /// </summary>
+        protected override object SyncRoot
+        {
+            get { return sync_root; }
+        }
+
+        #endregion
+
         #region --- GL Overloads ---
 
 #pragma warning disable 3019
diff --git a/Source/OpenTK/Platform/X11/GlxHelper.cs b/Source/OpenTK/Platform/X11/GlxHelper.cs
index 2094509b..3ec38c1b 100644
--- a/Source/OpenTK/Platform/X11/GlxHelper.cs
+++ b/Source/OpenTK/Platform/X11/GlxHelper.cs
@@ -18,10 +18,16 @@ namespace OpenTK.Platform.X11
     partial class Glx : BindingsBase
     {
         const string Library = "libGL.so.1";
+        static readonly object sync_root = new object();
 
         // Disable BeforeFieldInit optimization.
         static Glx() { }
 
+        protected override object SyncRoot
+        {
+            get { return sync_root; }
+        }
+
         protected override IntPtr GetAddress (string funcname)
         {
             return Glx.GetProcAddress(funcname);