diff --git a/mysys/mf_format.c b/mysys/mf_format.c
index 39084799563..aa4d469e20c 100644
--- a/mysys/mf_format.c
+++ b/mysys/mf_format.c
@@ -53,7 +53,8 @@ my_string fn_format(my_string to, const char *name, const char *dsk,
   name+=(length=dirname_part(dev,(startpos=(my_string) name)));
   if (length == 0 || flag & 1)
   {
-    (void) strmov(dev,dsk);			/* Use given directory */
+    (void) strnmov(dev,dsk, sizeof(dev) - 2);
+      /* Use given directory */
     convert_dirname(dev);			/* Fix to this OS */
   }
   if (flag & 8)
diff --git a/sql/ha_myisam.cc b/sql/ha_myisam.cc
index 8ffab93f0e0..aac53c5667d 100644
--- a/sql/ha_myisam.cc
+++ b/sql/ha_myisam.cc
@@ -333,21 +333,12 @@ int ha_myisam::restore(THD* thd, HA_CHECK_OPT *check_opt)
   HA_CHECK_OPT tmp_check_opt;
   char* backup_dir = thd->lex.backup_dir;
   char src_path[FN_REFLEN], dst_path[FN_REFLEN];
-  int backup_dir_len = strlen(backup_dir);
   char* table_name = table->real_name;
-  int table_name_len = strlen(table_name);
-  if(backup_dir_len + table_name_len + 4 >= FN_REFLEN)
+  if(!fn_format(src_path, table_name, backup_dir, MI_NAME_DEXT, 4 + 64))
     return HA_ADMIN_INVALID;
-  memcpy(src_path, backup_dir, backup_dir_len);
-  char* p = src_path + backup_dir_len;
-  *p++ = '/';
-  memcpy(p, table_name, table_name_len);
-  p += table_name_len;
-  *p = 0;
-  fn_format(src_path, src_path, "", MI_NAME_DEXT, 4);
 
   int error = 0;
-  char* errmsg = "";
+  const char* errmsg = "";
   
   if(my_copy(src_path, fn_format(dst_path, table->path, "",
 				 MI_NAME_DEXT, 4), MYF(MY_WME)))
@@ -378,28 +369,21 @@ int ha_myisam::backup(THD* thd, HA_CHECK_OPT *check_opt)
 {
   char* backup_dir = thd->lex.backup_dir;
   char src_path[FN_REFLEN], dst_path[FN_REFLEN];
-  int backup_dir_len = strlen(backup_dir);
   char* table_name = table->real_name;
-  int table_name_len = strlen(table_name);
-  if(backup_dir_len + table_name_len + 4 >= FN_REFLEN)
+  if(!fn_format(dst_path, table_name, backup_dir, reg_ext, 4 + 64))
     return HA_ADMIN_INVALID;
-  memcpy(dst_path, backup_dir, backup_dir_len);
-  char* p = dst_path + backup_dir_len;
-  *p++ = '/';
-  memcpy(p, table_name, table_name_len);
-  p += table_name_len;
-  *p = 0;
   if(my_copy(fn_format(src_path, table->path,"", reg_ext, 4),
-	     fn_format(dst_path, dst_path, "", reg_ext, 4),
+	     dst_path,
 	     MYF(MY_WME | MY_HOLD_ORIGINAL_MODES )))
     {
       return HA_ADMIN_FAILED;
     }
 
-  *p = 0;
-  *(fn_ext(src_path)) = 0;
-  if(my_copy(fn_format(src_path, src_path,"", MI_NAME_DEXT, 4),
-	     fn_format(dst_path, dst_path, "", MI_NAME_DEXT, 4),
+  if(!fn_format(dst_path, table_name, backup_dir, MI_NAME_DEXT, 4 + 64))
+    return HA_ADMIN_INVALID;
+
+  if(my_copy(fn_format(src_path, table->path,"", MI_NAME_DEXT, 4),
+	     dst_path,
 	     MYF(MY_WME | MY_HOLD_ORIGINAL_MODES ))  )
     return HA_ADMIN_FAILED;