diff --git a/Source/HBIOS/hbios.asm b/Source/HBIOS/hbios.asm
index 478bc971..10ca4b4f 100644
--- a/Source/HBIOS/hbios.asm
+++ b/Source/HBIOS/hbios.asm
@@ -1245,7 +1245,7 @@ HB_CPU1:
 	LD	(IVT(INT_TIM0)),HL	; Z180 TIMER 0
 
 	; SETUP PERIODIC TIMER INTERRUPT ON TIMER 0
-	LD	HL,(CB_CPUKHZ)		; 50HZ = 18432000 / 20 / 50 / X, SO X = CPU KHZ
+	LD	HL,__CPU_CLOCK/TICKSPERSEC/20-1	; 50HZ = 18432000/ 50 / 20
 	LD	B,0
 	LD	C,Z180_RLDR0L		; INITIALIZE TIMER 0 RELOAD REGISTER
 	OUT	(C),L