diff --git a/Source/OpenTK/Input/KeyboardState.cs b/Source/OpenTK/Input/KeyboardState.cs
index 91c019a8..612dc963 100644
--- a/Source/OpenTK/Input/KeyboardState.cs
+++ b/Source/OpenTK/Input/KeyboardState.cs
@@ -39,7 +39,8 @@ namespace OpenTK.Input
         #region Fields
 
         // Allocate enough ints to store all keyboard keys
-        const int NumInts = ((int)Key.LastKey + 31) / 32;
+        const int IntSize = sizeof(int);
+        const int NumInts = ((int)Key.LastKey + IntSize - 1) / IntSize;
         // The following line triggers bogus CS0214 in gmcs 2.0.1, sigh...
         unsafe fixed int Keys[NumInts];
 
@@ -47,6 +48,24 @@ namespace OpenTK.Input
 
         #region Public Members
 
+        /// <summary>
+        /// Gets a <see cref="System.Boolean"/> indicating whether the specified
+        /// <see cref="OpenTK.Input.Key"/> is pressed.
+        /// </summary>
+        /// <param name="key">The <see cref="OpenTK.Input.Key"/> to check.</param>
+        /// <returns>True if key is pressed; false otherwise.</returns>
+        public bool this[Key key]
+        {
+            get { return IsKeyDown(key); }
+            internal set
+            {
+                if (value)
+                    EnableBit((int)key);
+                else
+                    DisableBit((int)key);
+            }
+        }
+
         /// <summary>
         /// Gets a <see cref="System.Boolean"/> indicating whether this key is down.
         /// </summary>
@@ -71,6 +90,8 @@ namespace OpenTK.Input
 
         internal bool ReadBit(int offset)
         {
+            ValidateOffset(offset);
+
             int int_offset = offset / 32;
             int bit_offset = offset % 32;
             unsafe
@@ -84,6 +105,8 @@ namespace OpenTK.Input
 
         internal void EnableBit(int offset)
         {
+            ValidateOffset(offset);
+
             int int_offset = offset / 32;
             int bit_offset = offset % 32;
             unsafe
@@ -97,6 +120,8 @@ namespace OpenTK.Input
 
         internal void DisableBit(int offset)
         {
+            ValidateOffset(offset);
+
             int int_offset = offset / 32;
             int bit_offset = offset % 32;
             unsafe
@@ -110,6 +135,16 @@ namespace OpenTK.Input
 
         #endregion
 
+        #region Private Members
+
+        static void ValidateOffset(int offset)
+        {
+            if (offset < 0 || offset >= NumInts * IntSize)
+                throw new ArgumentOutOfRangeException("offset");
+        }
+
+        #endregion
+
         #region IEquatable<KeyboardState> Members
 
         /// <summary>
diff --git a/Source/OpenTK/Input/MouseState.cs b/Source/OpenTK/Input/MouseState.cs
index e0b5b458..a4449aad 100644
--- a/Source/OpenTK/Input/MouseState.cs
+++ b/Source/OpenTK/Input/MouseState.cs
@@ -39,7 +39,8 @@ namespace OpenTK.Input
         #region Fields
 
         // Allocate enough ints to store all mouse buttons
-        const int NumInts = ((int)MouseButton.LastButton + 31) / 32;
+        const int IntSize = sizeof(int);
+        const int NumInts = ((int)MouseButton.LastButton + IntSize - 1) / IntSize;
         // The following line triggers bogus CS0214 in gmcs 2.0.1, sigh...
         unsafe fixed int Buttons[NumInts];
         int x, y;
@@ -49,6 +50,24 @@ namespace OpenTK.Input
 
         #region Public Members
 
+        /// <summary>
+        /// Gets a <see cref="System.Boolean"/> indicating whether the specified
+        /// <see cref="OpenTK.Input.MouseButton"/> is pressed.
+        /// </summary>
+        /// <param name="button">The <see cref="OpenTK.Input.MouseButton"/> to check.</param>
+        /// <returns>True if key is pressed; false otherwise.</returns>
+        public bool this[MouseButton button]
+        {
+            get { return IsButtonDown(button); }
+            internal set
+            {
+                if (value)
+                    EnableBit((int)button);
+                else
+                    DisableBit((int)button);
+            }
+        }
+
         /// <summary>
         /// Gets a <see cref="System.Boolean"/> indicating whether this button is down.
         /// </summary>
@@ -106,19 +125,6 @@ namespace OpenTK.Input
             internal set { y = value; }
         }
 
-        /// <summary>
-        /// Gets a System.Boolean indicating the state of the specified MouseButton.
-        /// </summary>
-        /// <param name="button">The MouseButton to check.</param>
-        /// <returns>True if the MouseButton is pressed, false otherwise.</returns>
-        public bool this[MouseButton button]
-        {
-            get
-            {
-                return IsButtonDown(button);
-            }
-        }
-
         /// <summary>
         /// Gets a <see cref="System.Boolean" indicating whether the left mouse button is pressed.
         /// This property is intended for XNA compatibility.
@@ -251,6 +257,8 @@ namespace OpenTK.Input
 
         internal bool ReadBit(int offset)
         {
+            ValidateOffset(offset);
+
             int int_offset = offset / 32;
             int bit_offset = offset % 32;
             unsafe
@@ -264,6 +272,8 @@ namespace OpenTK.Input
 
         internal void EnableBit(int offset)
         {
+            ValidateOffset(offset);
+
             int int_offset = offset / 32;
             int bit_offset = offset % 32;
             unsafe
@@ -277,6 +287,8 @@ namespace OpenTK.Input
 
         internal void DisableBit(int offset)
         {
+            ValidateOffset(offset);
+
             int int_offset = offset / 32;
             int bit_offset = offset % 32;
             unsafe
@@ -290,6 +302,16 @@ namespace OpenTK.Input
 
         #endregion
 
+        #region Private Members
+
+        static void ValidateOffset(int offset)
+        {
+            if (offset < 0 || offset >= NumInts * IntSize)
+                throw new ArgumentOutOfRangeException("offset");
+        }
+
+        #endregion
+
         #region IEquatable<MouseState> Members
 
         /// <summary>