diff -urd -x prof -X freeciv.current/diff_ignore work/common/map.c no_check/common/map.c
--- work/common/map.c	Wed Sep 26 14:21:08 2001
+++ no_check/common/map.c	Wed Sep 26 18:31:26 2001
@@ -1289,7 +1289,9 @@
 
 int is_real_tile(int x, int y)
 {
-  return 0 <= y && y < map.ysize;
+  int x1 = x, y1 = y;
+
+  return normalize_map_pos(&x1, &y1);
 }
 
 /**************************************************************************
@@ -1302,10 +1304,7 @@
   while (*x >= map.xsize)
     *x -= map.xsize;
 
-  if (!is_real_tile(*x, *y))
-    return FALSE;
-
-  return TRUE;
+  return (0 <= *y && *y < map.ysize);
 }
 
 /**************************************************************************