diff --git a/shared-core/radeon_cp.c b/shared-core/radeon_cp.c
index da15a4b8..d6887f1f 100644
--- a/shared-core/radeon_cp.c
+++ b/shared-core/radeon_cp.c
@@ -16114,9 +16114,9 @@ static u32 R500_READ_MCIND(drm_radeon_private_t *dev_priv, int addr)
 static u32 RS400_READ_MCIND(drm_radeon_private_t *dev_priv, int addr)
 {
 	u32 ret;
-	RADEON_WRITE(RS400_NB_MC_INDEX, addr & 0x7f);
+	RADEON_WRITE(RS400_NB_MC_INDEX, addr & 0xff);
 	ret = RADEON_READ(RS400_NB_MC_DATA);
-	RADEON_WRITE(RS400_NB_MC_INDEX, 0x7f);
+	RADEON_WRITE(RS400_NB_MC_INDEX, 0xff);
 	return ret;
 }
 
diff --git a/shared-core/radeon_drv.h b/shared-core/radeon_drv.h
index e580e5c1..d5c8fc3e 100644
--- a/shared-core/radeon_drv.h
+++ b/shared-core/radeon_drv.h
@@ -1165,9 +1165,9 @@ do {								\
 #define RS400_WRITE_MCIND( addr, val )				\
 do {									\
 	RADEON_WRITE( RS400_NB_MC_INDEX,				\
-			((addr) & 0x7f) | RS400_NB_MC_IND_WR_EN);	\
+			((addr) & 0xff) | RS400_NB_MC_IND_WR_EN);	\
 	RADEON_WRITE( RS400_NB_MC_DATA, (val) );			\
-	RADEON_WRITE( RS400_NB_MC_INDEX, 0x7f );			\
+	RADEON_WRITE( RS400_NB_MC_INDEX, 0xff );			\
 } while (0)
 
 #define RS690_WRITE_MCIND( addr, val )					\