diff --git a/src/fpu/fpu_instructions.h b/src/fpu/fpu_instructions.h
index bfc564ef..8b608249 100644
--- a/src/fpu/fpu_instructions.h
+++ b/src/fpu/fpu_instructions.h
@@ -118,12 +118,16 @@ static void FPU_ST80(PhysPt addr,Bitu reg) {
 	} test;
 	Bit64s sign80 = (fpu.regs[reg].ll&LONGTYPE(0x8000000000000000))?1:0;
 	Bit64s exp80 =  fpu.regs[reg].ll&LONGTYPE(0x7ff0000000000000);
-	Bit64s exp80final = (exp80>>52) - BIAS64 + BIAS80;
+	Bit64s exp80final = (exp80>>52);
 	Bit64s mant80 = fpu.regs[reg].ll&LONGTYPE(0x000fffffffffffff);
 	Bit64s mant80final = (mant80 << 11);
-	// Elvira wants the 8 and tcalc doesn't 
-	if(fpu.regs[reg].d != 0) mant80final |= LONGTYPE(0x8000000000000000);
-	test.begin= (static_cast<Bit16s>(sign80)<<15)| static_cast<Bit16s>(exp80final);
+	if(fpu.regs[reg].d != 0){ //Zero is a special case
+		// Elvira wants the 8 and tcalc doesn't
+		mant80final |= LONGTYPE(0x8000000000000000);
+		//Ca-cyber doesn't like this when result is zero.
+		exp80final += (BIAS80 - BIAS64);
+	}
+	test.begin = (static_cast<Bit16s>(sign80)<<15)| static_cast<Bit16s>(exp80final);
 	test.eind.ll = mant80final;
 	mem_writed(addr,test.eind.l.lower);
 	mem_writed(addr+4,test.eind.l.upper);