diff --git a/nemu/src/monitor/sdb/watchpoint.c b/nemu/src/monitor/sdb/watchpoint.c
index d283a7d..103809d 100644
--- a/nemu/src/monitor/sdb/watchpoint.c
+++ b/nemu/src/monitor/sdb/watchpoint.c
@@ -62,7 +62,7 @@ bool wp_check_hit(void) {
 }
 
 static WP* del_wp(WP** head, WP* pos) {
-  for (WP** i = head; (*i) != NULL && (*i)->next != NULL; i = (WP**)*i) {
+  for (WP** i = head; (*i) != NULL; i = (WP**)*i) {
     if ((**i).NO == pos->NO) {
       WP* res = *i;
       *i = (*i)->next;
@@ -112,6 +112,7 @@ void free_wp(WP *_wp) {
   WP* wp = del_wp(&head, _wp);
   if (wp == NULL) {
     printf("free_wp: no such watchpoint\n");
+    return;
   }
   wp->next = free_;
   free_ = wp;