diff --git a/exosphere/src/bootup.c b/exosphere/src/bootup.c
index 6cfddf5d7..88bad9361 100644
--- a/exosphere/src/bootup.c
+++ b/exosphere/src/bootup.c
@@ -120,7 +120,11 @@ void bootup_misc_mmio(void) {
     MAKE_MC_REG(0x230) = 0xFFFFFFFF;
     MAKE_MC_REG(0x234) = 0xFFFFFFFF;
     MAKE_MC_REG(0xB98) = 0xFFFFFFFF;
-    MAKE_MC_REG(0x038) = 0xE;
+    if (exosphere_get_target_firmware() >= EXOSPHERE_TARGET_FIRMWARE_400) {
+        MAKE_MC_REG(0x038) = 0xE;
+    } else {
+        MAKE_MC_REG(0x038) = 0x0;
+    }
     MAKE_MC_REG(0x03C) = 0;
     MAKE_MC_REG(0x9E0) = 0;
     MAKE_MC_REG(0x9E4) = 0;
@@ -128,7 +132,9 @@ void bootup_misc_mmio(void) {
     MAKE_MC_REG(0x9EC) = 0;
     MAKE_MC_REG(0x9F0) = 0;
     MAKE_MC_REG(0x9F4) = 0;
-    MAKE_MC_REG(0x01C) = 0;
+    if (exosphere_get_target_firmware() >= EXOSPHERE_TARGET_FIRMWARE_400) {
+        MAKE_MC_REG(0x01C) = 0;
+    }
     MAKE_MC_REG(0x020) = 0;
     MAKE_MC_REG(0x014) = 0x30000030;
     MAKE_MC_REG(0x018) = 0x2800003F;