diff --git a/hardware.inc b/hardware.inc
index e1e3b2c..2c7fa6c 100644
--- a/hardware.inc
+++ b/hardware.inc
@@ -1037,6 +1037,9 @@ def BOOTUP_A_MGB equ $FF
     def BOOTUP_A_SGB  equ BOOTUP_A_DMG
     def BOOTUP_A_SGB2 equ BOOTUP_A_MGB
 
+; Register B = CPU qualifier
+def BOOTUP_B_DMG0 equ $FF
+
 ; Register B = CPU qualifier (if A is BOOTUP_A_CGB)
 def B_BOOTUP_B_AGB equ 0
     def BOOTUP_B_CGB equ 0 << B_BOOTUP_B_AGB