pkg_check_modules with "::" in prefix

I have a CMakeLists.txt statement that works with cmake 2.8.12.2 and 3.7.2 but fails with 3.9.0:

pkg_check_modules ("glog::glog" REQUIRED libglog)

I get error "syntax error, unexpected cal_SYMBOL, expecting } (36)"

I'm not getting any backward compat warnings, so I wonder if it should work with 3.9.0?

My coworker says he is also seeing the error with 3.8.2.

I made a simple test for this:

cmake_minimum_required (VERSION 2.8.12)
project (TEST)
find_package(PkgConfig REQUIRED)
pkg_check_modules ("glog::glog" REQUIRED libglog)

Here is some sample output for the 3 cmake versions noted above:

chuck@h0:/tmp/test/b % cat ../CMakeLists.txt
cmake_minimum_required (VERSION 2.8.12)
project (TEST)
find_package(PkgConfig REQUIRED)
pkg_check_modules ("glog::glog" REQUIRED libglog)
chuck@h0:/tmp/test/b % 
chuck@h0:/tmp/test/b % cmake --version
cmake version 3.9.0

CMake suite maintained and supported by Kitware (kitware.com/cmake).
chuck@h0:/tmp/test/b % cmake ..
-- The C compiler identification is GNU 4.8.4
-- The CXX compiler identification is GNU 4.8.4
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found PkgConfig: /usr/bin/pkg-config (found version "0.26") 
CMake Error at /tmp/cmake/share/cmake-3.9/Modules/FindPkgConfig.cmake:587 (if):
  Syntax error in cmake code at

    /tmp/cmake/share/cmake-3.9/Modules/FindPkgConfig.cmake:587

  when parsing string

    ${__pkg_config_arguments_glog::glog}

  syntax error, unexpected cal_SYMBOL, expecting } (36)
Call Stack (most recent call first):
  CMakeLists.txt:4 (pkg_check_modules)


-- Configuring incomplete, errors occurred!
See also "/tmp/test/b/CMakeFiles/CMakeOutput.log".
chuck@h0:/tmp/test/b % rm -rf *
chuck@h0:/tmp/test/b % 
chuck@h0:/tmp/test/b % /usr/bin/cmake --version
cmake version 2.8.12.2
chuck@h0:/tmp/test/b % /usr/bin/cmake ..
-- The C compiler identification is GNU 4.8.4
-- The CXX compiler identification is GNU 4.8.4
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Found PkgConfig: /usr/bin/pkg-config (found version "0.26") 
-- checking for module 'libglog'
--   found libglog, version 0.3.3
-- Configuring done
-- Generating done
-- Build files have been written to: /tmp/test/b
chuck@h0:/tmp/test/b % 
chuck@h0:/tmp/test/b % rm -rf *
chuck@h0:/tmp/test/b % 
chuck@h0:/tmp/test/b % /proj/TableFS/data/travis14/cache/bin/cmake --version
cmake version 3.7.2

CMake suite maintained and supported by Kitware (kitware.com/cmake).
chuck@h0:/tmp/test/b % /proj/TableFS/data/travis14/cache/bin/cmake ..
-- The C compiler identification is GNU 4.8.4
-- The CXX compiler identification is GNU 4.8.4
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found PkgConfig: /usr/bin/pkg-config (found version "0.26") 
-- Checking for module 'libglog'
--   Found libglog, version 0.3.3
-- Configuring done
-- Generating done
-- Build files have been written to: /tmp/test/b
chuck@h0:/tmp/test/b %