XF 1.5 Should not allow to post with same title.

[xfactormaster]

Some times, I am using the same title for many times, it is allowing now. But it should not allow, if the title is already exist.
I found one add-on merge similar threads, but my requirement is, it should not allow to create the new threads, if the title is already exist.
Please guide me how to fix it.

Thank you.

 

[Paul B]

That would require custom development.