diff --git a/src/vmsrc/lib6502/lib6502.c b/src/vmsrc/lib6502/lib6502.c
index 51006fb..8146406 100644
--- a/src/vmsrc/lib6502/lib6502.c
+++ b/src/vmsrc/lib6502/lib6502.c
@@ -177,16 +177,16 @@ typedef uint16_t word;
       }                                                                                        \
     else                                                                                \
       {                                                                                        \
-        int l, h, s;                                                                        \
+        int l, h, s, c;                                                                        \
         /* inelegant & slow, but consistent with the hw for illegal digits */                \
         l= (A & 0x0F) + (B & 0x0F) + getC();                                                \
         h= (A & 0xF0) + (B & 0xF0);                                                        \
         if (l >= 0x0A) { l -= 0x0A;  h += 0x10; }                                        \
-        if (h >= 0xA0) { h -= 0xA0; }                                                        \
+        if (h >= 0xA0) { h -= 0xA0; c = 1;}else{c = 0;}                                  \
         fetch();                                                                        \
         s= h | (l & 0x0F);                                                                \
         /* only C is valid on NMOS 6502 */                                                \
-        setNVZC(s & 0x80, !(((A ^ B) & 0x80) && ((A ^ s) & 0x80)), !s, !!(h & 0x80));        \
+        setNVZC(s & 0x80, !(((A ^ B) & 0x80) && ((A ^ s) & 0x80)), !s, /*!!(h & 0x80)*/c);   \
         A= s;                                                                                \
         tick(1);                                                                        \
         next();                                                                                \
@@ -210,16 +210,16 @@ typedef uint16_t word;
     else                                                                                \
       {                                                                                        \
         /* this is verbatim ADC, with a 10's complemented operand */                        \
-        int l, h, s;                                                                        \
+        int l, h, s, c;                                                                        \
         B= 0x99 - B;                                                                        \
         l= (A & 0x0F) + (B & 0x0F) + getC();                                                \
         h= (A & 0xF0) + (B & 0xF0);                                                        \
         if (l >= 0x0A) { l -= 0x0A;  h += 0x10; }                                        \
-        if (h >= 0xA0) { h -= 0xA0; }                                                        \
+        if (h >= 0xA0) { h -= 0xA0; c = 1;}else{c = 0;}                                    \
         fetch();                                                                        \
         s= h | (l & 0x0F);                                                                \
         /* only C is valid on NMOS 6502 */                                                \
-        setNVZC(s & 0x80, !(((A ^ B) & 0x80) && ((A ^ s) & 0x80)), !s, !!(h & 0x80));        \
+        setNVZC(s & 0x80, !(((A ^ B) & 0x80) && ((A ^ s) & 0x80)), !s, /*!!(h & 0x80)*/c);  \
         A= s;                                                                                \
         tick(1);                                                                        \
         next();                                                                                \