fix build issue with clang

pull request for https://github.com/Homebrew/homebrew/issues/31398 
@mikemcquaid Please see referred pull request - issue is submitted to the upstream. OSX 10.9/Apple LLVM version 5.1 (clang-503.0.40) (based on LLVM 3.4svn). But it does not matter, because it will fail with any clang, there is gcc-ism in the code.