diff --git a/Minecraft.Client/GameRenderer.cpp b/Minecraft.Client/GameRenderer.cpp
index 390f114de..34ef65a57 100644
--- a/Minecraft.Client/GameRenderer.cpp
+++ b/Minecraft.Client/GameRenderer.cpp
@@ -1147,7 +1147,7 @@ void GameRenderer::render(float a, bool bFirst)
 	if (mc->noRender) return;
 	GameRenderer::anaglyph3d = mc->options->anaglyph3d;
 
-	glViewport(0, 0, mc->width, mc->height);	// 4J - added
+	glViewport(0, 0, mc->width, mc->height);	// 4J - added (no-op on Win64, viewport set by StateSetViewport)
 	ScreenSizeCalculator ssc(mc->options, mc->width, mc->height);
 	int screenWidth = ssc.getWidth();
 	int screenHeight = ssc.getHeight();
diff --git a/Minecraft.Client/glWrapper.cpp b/Minecraft.Client/glWrapper.cpp
index a356e674c..65a496fa9 100644
--- a/Minecraft.Client/glWrapper.cpp
+++ b/Minecraft.Client/glWrapper.cpp
@@ -48,11 +48,12 @@ void glLoadIdentity()
 	RenderManager.MatrixSetIdentity();
 }
 
-// AAR - Use calculated aspect ratio to support dynamic resizing
-extern float g_iAspectRatio;
+// AAR - Use the aspect ratio passed by the caller.  For single-player this
+// equals g_iAspectRatio (screen width / height), but for split-screen
+// getFovAndAspect adjusts it to match the viewport dimensions.
 void gluPerspective(float fovy, float aspect, float zNear, float zFar)
 {
-	RenderManager.MatrixPerspective(fovy, g_iAspectRatio, zNear, zFar);
+	RenderManager.MatrixPerspective(fovy, aspect, zNear, zFar);
 }
 
 void glOrtho(float left,float right,float bottom,float top,float zNear,float zFar)