[Q] Help with unrooting Htc one mini(m4)

[altjim]

Hello guys,I have seen such a lot of posts and topics around here and i feel so lost.
So i want to unroot my Htc one mini and i am at the stage where i have locked the bootloader..It seems that there is not an available RUU that can unroot for me,but i can't find another way.The software number of my phone is 4.09.161.6 .
Please help i feel desperate!
Thank you in advance!!