From c62945af58c9d205db69e5887731c3b5e6c438c0 Mon Sep 17 00:00:00 2001
From: Gericom <fnouwt2@gmail.com>
Date: Sun, 11 Jan 2026 12:09:17 +0100
Subject: [PATCH] Lock scfg9 when switching to DS mode to avoid DSi mode being
 misdetected. Fixes #90.

---
 arm9/source/main.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arm9/source/main.cpp b/arm9/source/main.cpp
index 422d4ed..0695fbe 100644
--- a/arm9/source/main.cpp
+++ b/arm9/source/main.cpp
@@ -100,8 +100,8 @@ static void bootArm9()
 
     if (((REG_SCFG_EXT >> 14) & 3) == 0)
     {
-        // When switched to DS mode, disable vram extensions
-        REG_SCFG_EXT &= ~(1 << 13);
+        // When switched to DS mode, disable vram extensions and lock scfg9
+        REG_SCFG_EXT &= ~((1 << 13) | (1 << 31));
     }
 
     while (gfx_getVCount() != 191);