diff --git a/problems/面试题02.07.链表相交.md b/problems/面试题02.07.链表相交.md
index 0a38cc33..ba6631a4 100644
--- a/problems/面试题02.07.链表相交.md
+++ b/problems/面试题02.07.链表相交.md
@@ -160,6 +160,8 @@ class Solution:
         那么，只要其中一个链表走完了，就去走另一条链表的路。如果有交点，他们最终一定会在同一个
         位置相遇
         """
+        if headA is None or headB is None: 
+            return None
         cur_a, cur_b = headA, headB     # 用两个指针代替a和b