diff --git a/bn_mp_tc_and.c b/bn_mp_tc_and.c
index 0e28ca8..800681a 100644
--- a/bn_mp_tc_and.c
+++ b/bn_mp_tc_and.c
@@ -18,7 +18,7 @@ int mp_tc_and(const mp_int *a, const mp_int *b, mp_int *c)
 {
    int res = MP_OKAY, bits;
    int as = mp_isneg(a), bs = mp_isneg(b), s = 0;
-   mp_int *mx = 0, _mx, acpy, bcpy;
+   mp_int *mx = NULL, _mx, acpy, bcpy;
 
    if (as || bs) {
       bits = MAX(mp_count_bits(a), mp_count_bits(b));
diff --git a/bn_mp_tc_div_2d.c b/bn_mp_tc_div_2d.c
index 5ea4e38..f341c9b 100644
--- a/bn_mp_tc_div_2d.c
+++ b/bn_mp_tc_div_2d.c
@@ -18,7 +18,7 @@ int mp_tc_div_2d(const mp_int *a, int b, mp_int *c)
 {
   int res;
   if (!mp_isneg(a)) {
-    return mp_div_2d(a, b, c, 0);
+    return mp_div_2d(a, b, c, NULL);
   }
 
   res = mp_add_d(a, 1, c);
@@ -26,7 +26,7 @@ int mp_tc_div_2d(const mp_int *a, int b, mp_int *c)
     return res;
   }
 
-  res = mp_div_2d(c, b, c, 0);
+  res = mp_div_2d(c, b, c, NULL);
   return res == MP_OKAY ? mp_sub_d(c, 1, c) : res;
 }
 #endif
diff --git a/bn_mp_tc_or.c b/bn_mp_tc_or.c
index 1e7d583..344c20c 100644
--- a/bn_mp_tc_or.c
+++ b/bn_mp_tc_or.c
@@ -18,7 +18,7 @@ int mp_tc_or(const mp_int *a, const mp_int *b, mp_int *c)
 {
    int res = MP_OKAY, bits;
    int as = mp_isneg(a), bs = mp_isneg(b), s = 0;
-   mp_int *mx = 0, _mx, acpy, bcpy;
+   mp_int *mx = NULL, _mx, acpy, bcpy;
 
    if (as || bs) {
       bits = MAX(mp_count_bits(a), mp_count_bits(b));
diff --git a/bn_mp_tc_xor.c b/bn_mp_tc_xor.c
index be9b9d8..09547a5 100644
--- a/bn_mp_tc_xor.c
+++ b/bn_mp_tc_xor.c
@@ -18,7 +18,7 @@ int mp_tc_xor(const mp_int *a, const mp_int *b, mp_int *c)
 {
    int res = MP_OKAY, bits;
    int as = mp_isneg(a), bs = mp_isneg(b), s = 0;
-   mp_int *mx = 0, _mx, acpy, bcpy;
+   mp_int *mx = NULL, _mx, acpy, bcpy;
 
    if (as || bs) {
       bits = MAX(mp_count_bits(a), mp_count_bits(b));