Building on Appveyor: invalid escape sequence \L

CMake Error at C:/Program Files (x86)/CMake/share/cmake-3.8/Modules/FindBoost.cmake:912 (list):
  Syntax error in cmake code at
    C:/Program Files (x86)/CMake/share/cmake-3.8/Modules/FindBoost.cmake:912
  when parsing string
    C:\Libraries\boost_1_54_0/lib${_arch_suffix}-msvc-10.0
  Invalid character escape '\L'.
Call Stack (most recent call first):
  C:/Program Files (x86)/CMake/share/cmake-3.8/Modules/FindBoost.cmake:1380 (_Boost_UPDATE_WINDOWS_LIBRARY_SEARCH_DIRS_WITH_PREBUILT_PATHS)
  build/cmake/DefineOptions.cmake:53 (find_package)
  CMakeLists.txt:52 (include)