diff --git a/bn_fast_mp_invmod.c b/bn_fast_mp_invmod.c
index c595247..25e145b 100644
--- a/bn_fast_mp_invmod.c
+++ b/bn_fast_mp_invmod.c
@@ -27,7 +27,7 @@ int fast_mp_invmod (mp_int * a, mp_int * b, mp_int * c)
   int     res, neg;
 
   /* 2. [modified] b must be odd   */
-  if (mp_iseven (b) == 1) {
+  if (mp_iseven (b) == MP_YES) {
     return MP_VAL;
   }
 
@@ -57,13 +57,13 @@ int fast_mp_invmod (mp_int * a, mp_int * b, mp_int * c)
 
 top:
   /* 4.  while u is even do */
-  while (mp_iseven (&u) == 1) {
+  while (mp_iseven (&u) == MP_YES) {
     /* 4.1 u = u/2 */
     if ((res = mp_div_2 (&u, &u)) != MP_OKAY) {
       goto LBL_ERR;
     }
     /* 4.2 if B is odd then */
-    if (mp_isodd (&B) == 1) {
+    if (mp_isodd (&B) == MP_YES) {
       if ((res = mp_sub (&B, &x, &B)) != MP_OKAY) {
         goto LBL_ERR;
       }
@@ -75,13 +75,13 @@ top:
   }
 
   /* 5.  while v is even do */
-  while (mp_iseven (&v) == 1) {
+  while (mp_iseven (&v) == MP_YES) {
     /* 5.1 v = v/2 */
     if ((res = mp_div_2 (&v, &v)) != MP_OKAY) {
       goto LBL_ERR;
     }
     /* 5.2 if D is odd then */
-    if (mp_isodd (&D) == 1) {
+    if (mp_isodd (&D) == MP_YES) {
       /* D = (D-x)/2 */
       if ((res = mp_sub (&D, &x, &D)) != MP_OKAY) {
         goto LBL_ERR;
@@ -115,7 +115,7 @@ top:
   }
 
   /* if not zero goto step 4 */
-  if (mp_iszero (&u) == 0) {
+  if (mp_iszero (&u) == MP_NO) {
     goto top;
   }
 
diff --git a/bn_mp_cnt_lsb.c b/bn_mp_cnt_lsb.c
index d862762..92cc4e8 100644
--- a/bn_mp_cnt_lsb.c
+++ b/bn_mp_cnt_lsb.c
@@ -26,7 +26,7 @@ int mp_cnt_lsb(mp_int *a)
    mp_digit q, qq;
 
    /* easy out */
-   if (mp_iszero(a) == 1) {
+   if (mp_iszero(a) == MP_YES) {
       return 0;
    }
 
diff --git a/bn_mp_div.c b/bn_mp_div.c
index f50a8d7..c33fac8 100644
--- a/bn_mp_div.c
+++ b/bn_mp_div.c
@@ -24,7 +24,7 @@ int mp_div(mp_int * a, mp_int * b, mp_int * c, mp_int * d)
    int    res, n, n2;
 
   /* is divisor zero ? */
-  if (mp_iszero (b) == 1) {
+  if (mp_iszero (b) == MP_YES) {
     return MP_VAL;
   }
 
@@ -106,7 +106,7 @@ int mp_div (mp_int * a, mp_int * b, mp_int * c, mp_int * d)
   int     res, n, t, i, norm, neg;
 
   /* is divisor zero ? */
-  if (mp_iszero (b) == 1) {
+  if (mp_iszero (b) == MP_YES) {
     return MP_VAL;
   }
 
diff --git a/bn_mp_div_d.c b/bn_mp_div_d.c
index 55f3831..dbaeb10 100644
--- a/bn_mp_div_d.c
+++ b/bn_mp_div_d.c
@@ -47,7 +47,7 @@ int mp_div_d (mp_int * a, mp_digit b, mp_int * c, mp_digit * d)
   }
 
   /* quick outs */
-  if (b == 1 || mp_iszero(a) == 1) {
+  if (b == 1 || mp_iszero(a) == MP_YES) {
      if (d != NULL) {
         *d = 0;
      }
diff --git a/bn_mp_exptmod.c b/bn_mp_exptmod.c
index da0a8d3..1d9059e 100644
--- a/bn_mp_exptmod.c
+++ b/bn_mp_exptmod.c
@@ -89,7 +89,7 @@ int mp_exptmod (mp_int * G, mp_int * X, mp_int * P, mp_int * Y)
     
   /* if the modulus is odd or dr != 0 use the montgomery method */
 #ifdef BN_MP_EXPTMOD_FAST_C
-  if (mp_isodd (P) == 1 || dr !=  0) {
+  if (mp_isodd (P) == MP_YES || dr !=  0) {
     return mp_exptmod_fast (G, X, P, Y, dr);
   } else {
 #endif
diff --git a/bn_mp_gcd.c b/bn_mp_gcd.c
index 7d1c1c6..8cf6e00 100644
--- a/bn_mp_gcd.c
+++ b/bn_mp_gcd.c
@@ -70,7 +70,7 @@ int mp_gcd (mp_int * a, mp_int * b, mp_int * c)
      }
   }
 
-  while (mp_iszero(&v) == 0) {
+  while (mp_iszero(&v) == MP_NO) {
      /* make sure v is the largest */
      if (mp_cmp_mag(&u, &v) == MP_GT) {
         /* swap u and v to make sure v is >= u */
diff --git a/bn_mp_invmod.c b/bn_mp_invmod.c
index 67a9a61..c0eb2c0 100644
--- a/bn_mp_invmod.c
+++ b/bn_mp_invmod.c
@@ -19,13 +19,13 @@
 int mp_invmod (mp_int * a, mp_int * b, mp_int * c)
 {
   /* b cannot be negative */
-  if (b->sign == MP_NEG || mp_iszero(b) == 1) {
+  if (b->sign == MP_NEG || mp_iszero(b) == MP_YES) {
     return MP_VAL;
   }
 
 #ifdef BN_FAST_MP_INVMOD_C
   /* if the modulus is odd we can use a faster routine instead */
-  if (mp_isodd (b) == 1) {
+  if (mp_isodd (b) == MP_YES) {
     return fast_mp_invmod (a, b, c);
   }
 #endif
diff --git a/bn_mp_invmod_slow.c b/bn_mp_invmod_slow.c
index e0adda9..50ce2c1 100644
--- a/bn_mp_invmod_slow.c
+++ b/bn_mp_invmod_slow.c
@@ -22,7 +22,7 @@ int mp_invmod_slow (mp_int * a, mp_int * b, mp_int * c)
   int     res;
 
   /* b cannot be negative */
-  if (b->sign == MP_NEG || mp_iszero(b) == 1) {
+  if (b->sign == MP_NEG || mp_iszero(b) == MP_YES) {
     return MP_VAL;
   }
 
@@ -41,7 +41,7 @@ int mp_invmod_slow (mp_int * a, mp_int * b, mp_int * c)
   }
 
   /* 2. [modified] if x,y are both even then return an error! */
-  if (mp_iseven (&x) == 1 && mp_iseven (&y) == 1) {
+  if (mp_iseven (&x) == MP_YES && mp_iseven (&y) == MP_YES) {
     res = MP_VAL;
     goto LBL_ERR;
   }
@@ -58,13 +58,13 @@ int mp_invmod_slow (mp_int * a, mp_int * b, mp_int * c)
 
 top:
   /* 4.  while u is even do */
-  while (mp_iseven (&u) == 1) {
+  while (mp_iseven (&u) == MP_YES) {
     /* 4.1 u = u/2 */
     if ((res = mp_div_2 (&u, &u)) != MP_OKAY) {
       goto LBL_ERR;
     }
     /* 4.2 if A or B is odd then */
-    if (mp_isodd (&A) == 1 || mp_isodd (&B) == 1) {
+    if (mp_isodd (&A) == MP_YES || mp_isodd (&B) == MP_YES) {
       /* A = (A+y)/2, B = (B-x)/2 */
       if ((res = mp_add (&A, &y, &A)) != MP_OKAY) {
          goto LBL_ERR;
@@ -83,13 +83,13 @@ top:
   }
 
   /* 5.  while v is even do */
-  while (mp_iseven (&v) == 1) {
+  while (mp_iseven (&v) == MP_YES) {
     /* 5.1 v = v/2 */
     if ((res = mp_div_2 (&v, &v)) != MP_OKAY) {
       goto LBL_ERR;
     }
     /* 5.2 if C or D is odd then */
-    if (mp_isodd (&C) == 1 || mp_isodd (&D) == 1) {
+    if (mp_isodd (&C) == MP_YES || mp_isodd (&D) == MP_YES) {
       /* C = (C+y)/2, D = (D-x)/2 */
       if ((res = mp_add (&C, &y, &C)) != MP_OKAY) {
          goto LBL_ERR;
@@ -137,7 +137,7 @@ top:
   }
 
   /* if not zero goto step 4 */
-  if (mp_iszero (&u) == 0)
+  if (mp_iszero (&u) == MP_NO)
     goto top;
 
   /* now a = C, b = D, gcd == g*v */
diff --git a/bn_mp_jacobi.c b/bn_mp_jacobi.c
index b0722df..b8427a5 100644
--- a/bn_mp_jacobi.c
+++ b/bn_mp_jacobi.c
@@ -30,7 +30,7 @@ int mp_jacobi (mp_int * a, mp_int * p, int *c)
   }
 
   /* step 1.  if a == 0, return 0 */
-  if (mp_iszero (a) == 1) {
+  if (mp_iszero (a) == MP_YES) {
     *c = 0;
     return MP_OKAY;
   }
diff --git a/bn_mp_prime_next_prime.c b/bn_mp_prime_next_prime.c
index e306f3b..a977a44 100644
--- a/bn_mp_prime_next_prime.c
+++ b/bn_mp_prime_next_prime.c
@@ -84,7 +84,7 @@ int mp_prime_next_prime(mp_int *a, int t, int bbs_style)
          if ((err = mp_sub_d(a, (a->dp[0] & 3) + 1, a)) != MP_OKAY) { return err; };
       }
    } else {
-      if (mp_iseven(a) == 1) {
+      if (mp_iseven(a) == MP_YES) {
          /* force odd */
          if ((err = mp_sub_d(a, 1, a)) != MP_OKAY) {
             return err;
diff --git a/bn_mp_read_radix.c b/bn_mp_read_radix.c
index 8d3c710..d407e9d 100644
--- a/bn_mp_read_radix.c
+++ b/bn_mp_read_radix.c
@@ -73,7 +73,7 @@ int mp_read_radix (mp_int * a, const char *str, int radix)
   }
   
   /* set the sign only if a != 0 */
-  if (mp_iszero(a) != 1) {
+  if (mp_iszero(a) != MP_YES) {
      a->sign = neg;
   }
   return MP_OKAY;
diff --git a/bn_mp_to_unsigned_bin.c b/bn_mp_to_unsigned_bin.c
index 9655b31..132a6ca 100644
--- a/bn_mp_to_unsigned_bin.c
+++ b/bn_mp_to_unsigned_bin.c
@@ -26,7 +26,7 @@ int mp_to_unsigned_bin (mp_int * a, unsigned char *b)
   }
 
   x = 0;
-  while (mp_iszero (&t) == 0) {
+  while (mp_iszero (&t) == MP_NO) {
 #ifndef MP_8BIT
       b[x++] = (unsigned char) (t.dp[0] & 255);
 #else
diff --git a/bn_mp_toradix.c b/bn_mp_toradix.c
index f14fd07..94efc7a 100644
--- a/bn_mp_toradix.c
+++ b/bn_mp_toradix.c
@@ -29,7 +29,7 @@ int mp_toradix (mp_int * a, char *str, int radix)
   }
 
   /* quick out if its zero */
-  if (mp_iszero(a) == 1) {
+  if (mp_iszero(a) == MP_YES) {
      *str++ = '0';
      *str = '\0';
      return MP_OKAY;
@@ -47,7 +47,7 @@ int mp_toradix (mp_int * a, char *str, int radix)
   }
 
   digs = 0;
-  while (mp_iszero (&t) == 0) {
+  while (mp_iszero (&t) == MP_NO) {
     if ((res = mp_div_d (&t, (mp_digit) radix, &t, &d)) != MP_OKAY) {
       mp_clear (&t);
       return res;
diff --git a/bn_mp_toradix_n.c b/bn_mp_toradix_n.c
index 173372b..eb8195f 100644
--- a/bn_mp_toradix_n.c
+++ b/bn_mp_toradix_n.c
@@ -56,7 +56,7 @@ int mp_toradix_n(mp_int * a, char *str, int radix, int maxlen)
   }
 
   digs = 0;
-  while (mp_iszero (&t) == 0) {
+  while (mp_iszero (&t) == MP_NO) {
     if (--maxlen < 1) {
        /* no more room */
        break;