Vayve condemn bug with Rengar in bush

Yesterday I played Vayne, when Rengar came to gank me I went in the bottom bush to ambush him. When he appeared in the bush with his ult, I condemned him into the wall, but he simply jumped on me with his passive like he wasn't stunned. The stun particle over his head was visible tho, so it must be a bug. Regards SedimxD