ExternalProject: Additional command specified by COMMAND stop working

Project:

cmake_minimum_required(VERSION 3.0)
project(foo)

include(ExternalProject)

ExternalProject_Add(
    Foo
    DOWNLOAD_COMMAND
    ""
    CONFIGURE_COMMAND
    "${CMAKE_COMMAND}" -E echo "part 1"
    COMMAND
    "${CMAKE_COMMAND}" -E echo "part 2" ### <<<<<< Command lost!
    BUILD_COMMAND
    ""
    INSTALL_COMMAND
    ""
)

Works with CMake 3.9.1:

> cmake --version
cmake version 3.9.1

> rm -rf _builds
> cmake -H. -B_builds
> cmake --build _builds
...
[ 62%] Performing configure step for 'Foo'
part 1
part 2
[ 75%] No build step for 'Foo'
...

Current version from branch master:

> cmake --version
cmake version 3.9.20170823

> rm -rf _builds
> cmake -H. -B_builds
> cmake --build _builds
...
[ 62%] Performing configure step for 'Foo'
part 1
[ 75%] No build step for 'Foo'
...