c3-lang/libtommath

diff --git a/bn_mp_fread.c b/bn_mp_fread.c
index 04a1316..52ea773 100644
--- a/bn_mp_fread.c
+++ b/bn_mp_fread.c
@@ -49,7 +49,7 @@ mp_err mp_fread(mp_int *a, int radix, FILE *stream)
       }
    } while ((ch = fgetc(stream)) != EOF);
 
-   if (!mp_iszero(a)) {
+   if (a->used != 0) {
       a->sign = neg;
    }
 
diff --git a/tommath_class.h b/tommath_class.h
index 5f148cd..b72f545 100644
--- a/tommath_class.h
+++ b/tommath_class.h
@@ -401,7 +401,6 @@
 #   define BN_MP_ZERO_C
 #   define BN_MP_MUL_D_C
 #   define BN_MP_ADD_D_C
-#   define BN_MP_ISZERO_C
 #endif
 
 #if defined(BN_MP_FWRITE_C)