diff --git a/headers/private/graphics/radeon_hd/rhd_regs.h b/headers/private/graphics/radeon_hd/rhd_regs.h
index ba474df3c1..a41bdee5c1 100644
--- a/headers/private/graphics/radeon_hd/rhd_regs.h
+++ b/headers/private/graphics/radeon_hd/rhd_regs.h
@@ -240,6 +240,7 @@ enum {
     D2GRPH_LUT_SEL                 = 0x6908,
     D2GRPH_SWAP_CNTL               = 0x690C,
     D2GRPH_PRIMARY_SURFACE_ADDRESS = 0x6910,
+    D2GRPH_SECONDARY_SURFACE_ADDRESS = 0x6918,
     D2GRPH_PITCH                   = 0x6920,
     D2GRPH_SURFACE_OFFSET_X        = 0x6924,
     D2GRPH_SURFACE_OFFSET_Y        = 0x6928,