FindHDF5 ignores preset HDF5_DIR

Setting HDF5_DIR has no effect. This might be because FindHDF5.cmake only checks HDF5_ROOT when trying to find a CONFIG version:

if(HDF5_ROOT)
    set(_HDF5_SEARCH_OPTS NO_DEFAULT_PATH)
else()
    set(_HDF5_SEARCH_OPTS)
endif()

# Try to find HDF5 using an installed hdf5-config.cmake
if(NOT HDF5_FOUND AND NOT HDF5_NO_FIND_PACKAGE_CONFIG_FILE)
    find_package(HDF5 QUIET NO_MODULE
      HINTS "${HDF5_ROOT}"
      ${_HDF5_SEARCH_OPTS}
      ) 
...

Nevertheless, even when setting HDF5_ROOT (or when changing the above code) the above find_package only finds my system-version of hdf5-config.cmake (i.e., the one installed in c:\Program Files) and refuses to find my own installed version whatever I do with HDF5_ROOT and HDF5_DIR (I tried on Windows with CMake 3.9-rc5). If I remove the QUIET option in the find_package statement above, I get the confusing message

Could NOT find HDF5 (missing: HDF5_DIR)

even if HDF5_DIR is set.

It seems that I still don't understand find_package and Config files...