diff --git a/Source/HBIOS/plt_rc.inc b/Source/HBIOS/plt_rc.inc
index 6ca2d4b6..49bd0aa1 100644
--- a/Source/HBIOS/plt_rc.inc
+++ b/Source/HBIOS/plt_rc.inc
@@ -8,4 +8,4 @@ MPGSEL_3	.EQU	$7B	; BANK_3 PAGE SELECT REGISTER (WRITE ONLY)
 MPGENA		.EQU	$7C	; PAGING ENABLE REGISTER - BIT 0 = 1  (WRITE ONLY)
 ;
 RTC	    	.EQU	$C0	; RTC PORT address
-ZSIOBASE 	.EQU 	$80 ; RC OR SMB SIO DEFAULT
+SIOBASE 	.EQU 	$80 ; RC OR SMB SIO DEFAULT