diff --git a/cv4/a_train.c b/cv4/a_train.c
index 290ed95..db20e3a 100755
--- a/cv4/a_train.c
+++ b/cv4/a_train.c
@@ -40,6 +40,9 @@ void cancel_train(struct car* first) {
 
 struct car* clear_train(struct car* first, const char* target) {
 	struct car* this = first;
+	if (this == NULL){
+		return NULL;
+	}
 	while( this->next->next != NULL){
 		if(strcmp(this->value, target) == 0){
 			this->next == this->next->next;