clang-analyzer-alpha.unix.PthreadLock check missing from clang-tidy version 3.8 and 4.0?

I am trying to modernize my module's C++ source code using clang-tidy. A few weeks ago, I downloaded and built clang and clang tools version 3.9 and when I ran it on one of my cpp files I got clang-analyzer-alpha.unix.PthreadLock saying that lock has already been taken.

Later, because of space constraints I removed that version of clang and used version 3.8 and 4.0 available in our 3rd party repos.

In both of these versions, I did not get any warnings regarding this alpha check. How do I enable it in version 4.0 ?

I am already using -checks=* while analyzing/running clang-tidy on my cpp file.