diff --git a/mpi/mpi-cmp.c b/mpi/mpi-cmp.c
index 66e09612..8927fa0e 100644
--- a/mpi/mpi-cmp.c
+++ b/mpi/mpi-cmp.c
@@ -1,127 +1,130 @@
 /* mpi-cmp.c  -  MPI functions
  * Copyright (C) 1998, 1999, 2001, 2002, 2005 Free Software Foundation, Inc.
  *
  * This file is part of Libgcrypt.
  *
  * Libgcrypt is free software; you can redistribute it and/or modify
  * it under the terms of the GNU Lesser General Public License as
  * published by the Free Software Foundation; either version 2.1 of
  * the License, or (at your option) any later version.
  *
  * Libgcrypt is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 
 #include <config.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include "mpi-internal.h"
 
 int
 _gcry_mpi_cmp_ui (gcry_mpi_t u, unsigned long v)
 {
   mpi_limb_t limb = v;
 
   _gcry_mpi_normalize (u);
 
   /* Handle the case that U contains no limb.  */
   if (u->nlimbs == 0)
     return -(limb != 0);
 
   /* Handle the case that U is negative.  */
   if (u->sign)
     return -1;
 
   if (u->nlimbs == 1)
     {
       /* Handle the case that U contains exactly one limb.  */
 
       if (u->d[0] > limb)
 	return 1;
       if (u->d[0] < limb)
 	return -1;
       return 0;
     }
   else
     /* Handle the case that U contains more than one limb.  */
     return 1;
 }
 
 
 /* Helper for _gcry_mpi_cmp and _gcry_mpi_cmpabs.  */
 static int
 do_mpi_cmp (gcry_mpi_t u, gcry_mpi_t v, int absmode)
 {
   mpi_size_t usize;
   mpi_size_t vsize;
   int usign;
   int vsign;
   int cmp;
 
   if (mpi_is_opaque (u) || mpi_is_opaque (v))
     {
       /* We have no signan and thus ABSMODE has no efeect here.  */
       if (mpi_is_opaque (u) && !mpi_is_opaque (v))
         return -1;
       if (!mpi_is_opaque (u) && mpi_is_opaque (v))
         return 1;
       if (!u->sign && !v->sign)
         return 0; /* Empty buffers are identical.  */
       if (u->sign < v->sign)
         return -1;
       if (u->sign > v->sign)
         return 1;
       return memcmp (u->d, v->d, (u->sign+7)/8);
     }
   else
     {
       _gcry_mpi_normalize (u);
       _gcry_mpi_normalize (v);
 
       usize = u->nlimbs;
       vsize = v->nlimbs;
       usign = absmode? 0 : u->sign;
       vsign = absmode? 0 : v->sign;
 
-      /* Compare sign bits.  */
+      /* Special treatment for +0 == -0 */
+      if (!usize && !vsize)
+        return 0;
 
+      /* Compare sign bits.  */
       if (!usign && vsign)
         return 1;
       if (usign && !vsign)
         return -1;
 
       /* U and V are either both positive or both negative.  */
 
       if (usize != vsize && !usign && !vsign)
         return usize - vsize;
       if (usize != vsize && usign && vsign)
         return vsize + usize;
       if (!usize )
         return 0;
       if (!(cmp = _gcry_mpih_cmp (u->d, v->d, usize)))
         return 0;
       if ((cmp < 0?1:0) == (usign?1:0))
         return 1;
     }
   return -1;
 }
 
 
 int
 _gcry_mpi_cmp (gcry_mpi_t u, gcry_mpi_t v)
 {
   return do_mpi_cmp (u, v, 0);
 }
 
 /* Compare only the absolute values.  */
 int
 _gcry_mpi_cmpabs (gcry_mpi_t u, gcry_mpi_t v)
 {
   return do_mpi_cmp (u, v, 1);
 }