diff --git a/Tools/gdomap.c b/Tools/gdomap.c
index 329fc869d..b458fffad 100644
--- a/Tools/gdomap.c
+++ b/Tools/gdomap.c
@@ -655,7 +655,7 @@ map_add(uptr n, unsigned char l, unsigned int p, unsigned char t)
   m->svc = (t & GDO_SVC_MASK);
   memcpy(m->name, n, l);
 
-  if (map_used + 1 >= map_size)
+  if (map_used >= map_size)
     {
       if (map_size)
 	{
@@ -674,7 +674,7 @@ map_add(uptr n, unsigned char l, unsigned int p, unsigned char t)
 	{
 	  int	j;
 
-	  for (j = map_used+1; j > i; j--)
+	  for (j = map_used; j > i; j--)
 	    {
 	      map[j] = map[j-1];
 	    }