diff --git a/sources/Z80.c b/sources/Z80.c
index f0a4966..6963c7a 100644
--- a/sources/Z80.c
+++ b/sources/Z80.c
@@ -178,7 +178,7 @@ static zuint8 const pf_parity_table[256] = {
 #define PF_PARITY(value) pf_parity_table[value]
 
 #define VF(function, operand)					     \
-static Z_INLINE zuint8 pf_overflow_##function##8(zuint8 a, zuint8 b) \
+static Z_INLINE zuint8 pf_overflow_##function##8(zsint8 a, zsint8 b) \
 	{							     \
 	zsint total = ((zsint)a) operand ((zsint)b);		     \
 								     \
@@ -190,7 +190,7 @@ VF(sub, -)
 
 #undef	VF
 #define VF(function, bits, type, operand, minimum, maximum)					\
-static Z_INLINE zuint8 pf_overflow_##function##bits(zuint##bits a, zuint##bits b, zuint8 carry) \
+static Z_INLINE zuint8 pf_overflow_##function##bits(zsint##bits a, zsint##bits b, zuint8 carry) \
 	{											\
 	type total = ((type)a) operand ((type)b) operand carry;					\
 												\