ret = -ENOSPC;
                        goto err;
-               } else if (!tmp_e && old_fm) {
+               } else if (!tmp_e && old_fm && old_fm->e[i]) {
                        ret = erase_block(ubi, old_fm->e[i]->pnum);
                        if (ret < 0) {
                                int j;
                } else {
                        new_fm->e[i] = tmp_e;
 
-                       if (old_fm)
+                       if (old_fm && old_fm->e[i])
                                ubi_wl_put_fm_peb(ubi, old_fm->e[i], i,
                                                  old_fm->to_be_tortured[i]);
                }
        }
 
+       /* Old fastmap is larger than the new one */
+       if (old_fm && new_fm->used_blocks < old_fm->used_blocks) {
+               for (i = new_fm->used_blocks; i < old_fm->used_blocks; i++) {
+                       ubi_wl_put_fm_peb(ubi, old_fm->e[i], i,
+                                         old_fm->to_be_tortured[i]);
+               }
+       }
+
        spin_lock(&ubi->wl_lock);
        tmp_e = ubi_wl_get_fm_peb(ubi, 1);
        spin_unlock(&ubi->wl_lock);