下面的代码片段用于反转单链表，请选出正确修改使其能正确实现相应功能。

ListNode* reverseLinkedList(ListNode* head) {
 ListNode* prev = nullptr;
 ListNode* current = head;
 while (current != nullptr) {
  ListNode* next = current->next;
  current->next = next;
  prev = current;
  current = next;
 }
 return prev;
}