亡羊补牢

wángyáng-bǔláo

[mend the fold after a sheep is lost; shut the stable when the horse is tolen] 羊丢失以后, 才修补羊圈。 比喻发生问题及时采取善后措施, 以免酿成大错

亡羊补牢, 犹未为晚