diff --git a/lib/nettle/wmnaf.c b/lib/nettle/wmnaf.c
index 778518a..d9e4cef 100644
--- a/lib/nettle/wmnaf.c
+++ b/lib/nettle/wmnaf.c
@@ -33,6 +33,7 @@
 
 #define ABS(x) ((x) >= 0 ? (x) : -(x))
 
+#if 0
 /*
  * A local replacement for mpz_tstbit.
  * It is needed because for negative numbers original mpz_tstbit
@@ -58,6 +59,7 @@ mpz_unitstbit (mpz_srcptr u, mp_bitcnt_t bit_index)
 
   return (limb >> (bit_index % GMP_NUMB_BITS)) & 1;
 }
+#endif
 
 /*
  * Return an array with wMNAF representation together with its length.
@@ -96,6 +98,8 @@ ecc_wMNAF (mpz_t x, size_t * wmnaf_len)
       goto done;
     }
 
+  x->_mp_size *= sign;
+
   /* total number of bits */
   len = mpz_sizeinbase (x, 2);
 
@@ -135,7 +139,7 @@ ecc_wMNAF (mpz_t x, size_t * wmnaf_len)
 
       /* fill c with next LSB */
       c >>= 1;
-      c += BASEW * mpz_unitstbit (x, i + WMNAF_WINSIZE);
+      c += BASEW * mpz_tstbit (x, i + WMNAF_WINSIZE);
     }
 
   *wmnaf_len = i--;
@@ -150,5 +154,6 @@ ecc_wMNAF (mpz_t x, size_t * wmnaf_len)
       *wmnaf_len = i;
     }
 done:
+  x->_mp_size *= sign;
   return ret;
 }