diff --git a/src/Graphics/GraphicsDevice.cs b/src/Graphics/GraphicsDevice.cs
index 808d074..84eb327 100644
--- a/src/Graphics/GraphicsDevice.cs
+++ b/src/Graphics/GraphicsDevice.cs
@@ -386,6 +386,10 @@ namespace Microsoft.Xna.Framework.Graphics
 			// Set up the OpenGL Device. Loads entry points.
 			GLDevice = new OpenGLDevice(PresentationParameters);
 
+			// The mouse needs to know this for faux-backbuffer mouse scaling.
+			Input.Mouse.INTERNAL_BackBufferWidth = PresentationParameters.BackBufferWidth;
+			Input.Mouse.INTERNAL_BackBufferHeight = PresentationParameters.BackBufferHeight;
+
 			// Force set the default render states.
 			BlendState = BlendState.Opaque;
 			DepthStencilState = DepthStencilState.Default;
@@ -634,6 +638,10 @@ namespace Microsoft.Xna.Framework.Graphics
 				RenderTargetCount > 0
 			);
 
+			// The mouse needs to know this for faux-backbuffer mouse scaling.
+			Input.Mouse.INTERNAL_BackBufferWidth = PresentationParameters.BackBufferWidth;
+			Input.Mouse.INTERNAL_BackBufferHeight = PresentationParameters.BackBufferHeight;
+
 #if WIIU_GAMEPAD
 			wiiuPixelData = new byte[
 				PresentationParameters.BackBufferWidth *
diff --git a/src/Input/Mouse.cs b/src/Input/Mouse.cs
index cfde819..29baec4 100644
--- a/src/Input/Mouse.cs
+++ b/src/Input/Mouse.cs
@@ -30,8 +30,10 @@ namespace Microsoft.Xna.Framework.Input
 
 		#region Internal Variables
 
-		internal static int INTERNAL_WindowWidth = 800;
-		internal static int INTERNAL_WindowHeight = 600;
+		internal static int INTERNAL_WindowWidth = GraphicsDeviceManager.DefaultBackBufferWidth;
+		internal static int INTERNAL_WindowHeight = GraphicsDeviceManager.DefaultBackBufferHeight;
+		internal static int INTERNAL_BackBufferWidth = GraphicsDeviceManager.DefaultBackBufferWidth;
+		internal static int INTERNAL_BackBufferHeight = GraphicsDeviceManager.DefaultBackBufferHeight;
 
 		internal static int INTERNAL_MouseWheel = 0;
 
@@ -73,8 +75,8 @@ namespace Microsoft.Xna.Framework.Input
 			else
 			{
 				// Scale the mouse coordinates for the faux-backbuffer
-				x = (int) ((double) x * Game.Instance.GraphicsDevice.GLDevice.Backbuffer.Width / INTERNAL_WindowWidth);
-				y = (int) ((double) y * Game.Instance.GraphicsDevice.GLDevice.Backbuffer.Height / INTERNAL_WindowHeight);
+				x = (int) ((double) x * INTERNAL_BackBufferWidth / INTERNAL_WindowWidth);
+				y = (int) ((double) y * INTERNAL_BackBufferHeight / INTERNAL_WindowHeight);
 			}
 
 			return new MouseState(
@@ -101,8 +103,8 @@ namespace Microsoft.Xna.Framework.Input
 			INTERNAL_warpY = y;
 
 			// Scale the mouse coordinates for the faux-backbuffer
-			x = (int) ((double) x * INTERNAL_WindowWidth / Game.Instance.GraphicsDevice.GLDevice.Backbuffer.Width);
-			y = (int) ((double) y * INTERNAL_WindowHeight / Game.Instance.GraphicsDevice.GLDevice.Backbuffer.Height);
+			x = (int) ((double) x * INTERNAL_WindowWidth / INTERNAL_BackBufferWidth);
+			y = (int) ((double) y * INTERNAL_WindowHeight / INTERNAL_BackBufferHeight);
 
 			FNAPlatform.SetMousePosition(WindowHandle, x, y);
 			INTERNAL_IsWarped = true;