diff --git a/CMakeExternals/Boost.cmake b/CMakeExternals/Boost.cmake
index 363c93c430..073051c2e0 100644
--- a/CMakeExternals/Boost.cmake
+++ b/CMakeExternals/Boost.cmake
@@ -1,114 +1,115 @@
 #-----------------------------------------------------------------------------
 # Boost
 #-----------------------------------------------------------------------------
 
 if(MITK_USE_Boost)
 
   # Sanity checks
   if(DEFINED BOOST_ROOT AND NOT EXISTS ${BOOST_ROOT})
     message(FATAL_ERROR "BOOST_ROOT variable is defined but corresponds to non-existing directory")
   endif()
 
+  string(REPLACE "^^" ";" MITK_USE_Boost_LIBRARIES "${MITK_USE_Boost_LIBRARIES}")
+
   set(proj Boost)
   set(proj_DEPENDENCIES )
   set(Boost_DEPENDS ${proj})
 
   if(NOT DEFINED BOOST_ROOT AND NOT MITK_USE_SYSTEM_Boost)
 
     set(_boost_libs )
     set(INSTALL_COMMAND "")
 
     if(MITK_USE_Boost_LIBRARIES)
 
       # Set the boost root to the libraries install directory
       set(BOOST_ROOT "${CMAKE_CURRENT_BINARY_DIR}/${proj}-install")
 
       # We need binary boost libraries
-      string(REPLACE "^^" ";" MITK_USE_Boost_LIBRARIES "${MITK_USE_Boost_LIBRARIES}")
       foreach(_boost_lib ${MITK_USE_Boost_LIBRARIES})
         set(_boost_libs ${_boost_libs} --with-${_boost_lib})
       endforeach()
 
       if(WIN32)
         set(_boost_variant "")
         set(_shell_extension .bat)
         if(CMAKE_SIZEOF_VOID_P EQUAL 8)
           set(_boost_address_model "address-model=64")
         else()
           set(_boost_address_model "address-model=32")
         endif()
         if(MSVC)
           if(MSVC_VERSION EQUAL 1400)
             set(_boost_toolset "toolset=msvc-8.0")
           elseif(MSVC_VERSION EQUAL 1500)
             set(_boost_toolset "toolset=msvc-9.0")
           elseif(MSVC_VERSION EQUAL 1600)
             set(_boost_toolset "toolset=msvc-10.0")
           elseif(MSVC_VERSION EQUAL 1700)
             set(_boost_toolset "toolset=msvc-11.0")
           endif()
         endif()
       else()
         if(CMAKE_BUILD_TYPE STREQUAL "Debug")
           set(_boost_variant "variant=debug")
         else()
           set(_boost_variant "variant=release")
         endif()
         set(_shell_extension .sh)
       endif()
 
       if(APPLE)
         set(APPLE_CMAKE_SCRIPT ${CMAKE_CURRENT_BINARY_DIR}/${proj}-cmake/ChangeBoostLibsInstallNameForMac.cmake)
         configure_file(${CMAKE_CURRENT_SOURCE_DIR}/CMakeExternals/ChangeBoostLibsInstallNameForMac.cmake.in ${APPLE_CMAKE_SCRIPT} @ONLY)
         set(INSTALL_COMMAND ${CMAKE_COMMAND} -P ${APPLE_CMAKE_SCRIPT})
 
         # If compiler is clang (for newer clang versions boost does not compile with libc++)
         set(APPLE_CLANG_FLAGS)
         if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
           set(APPLE_CLANG_FLAGS toolset=clang cxxflags="-stdlib=libstdc++" linkflags="-stdlib=libstdc++")
         endif()
 
         # If is specific OSX_SYSROOT is set
         set (APPLE_SYSROOT_FLAG)
         if (NOT ${CMAKE_OSX_SYSROOT} STREQUAL "")
           set (APPLE_SYSROOT_FLAG --sysroot=${CMAKE_OSX_SYSROOT})
         endif()
 
         # Set the boost build command for apple
         set(_boost_build_cmd ${CMAKE_CURRENT_BINARY_DIR}/${proj}-src/bjam ${APPLE_SYSROOT_FLAG} --builddir=${CMAKE_CURRENT_BINARY_DIR}/${proj}-build --prefix=${CMAKE_CURRENT_BINARY_DIR}/${proj}-install
             ${_boost_toolset} ${_boost_address_model} ${_boost_variant} ${_boost_libs} link=shared,static threading=multi runtime-link=shared ${APPLE_CLANG_FLAGS} -q install)
       else()
         set(_boost_build_cmd ${CMAKE_CURRENT_BINARY_DIR}/${proj}-src/bjam --build-dir=${CMAKE_CURRENT_BINARY_DIR}/${proj}-build --prefix=${CMAKE_CURRENT_BINARY_DIR}/${proj}-install ${_boost_toolset} ${_boost_address_model}
             ${_boost_variant} ${_boost_libs} link=shared,static threading=multi runtime-link=shared -q install)
       endif()
 
       set(_boost_cfg_cmd ${CMAKE_CURRENT_BINARY_DIR}/${proj}-src/bootstrap${_shell_extension})
 
     else()
       # If no libraries are specified set the boost root to the boost src directory
       set(BOOST_ROOT "${CMAKE_CURRENT_BINARY_DIR}/${proj}-src")
       set(_boost_cfg_cmd )
       set(_boost_build_cmd )
     endif()
 
     ExternalProject_Add(${proj}
       SOURCE_DIR ${CMAKE_BINARY_DIR}/${proj}-src
       # Boost needs in-source builds
       BINARY_DIR ${proj}-src
       PREFIX ${proj}-cmake
       URL ${MITK_THIRDPARTY_DOWNLOAD_PREFIX_URL}/boost_1_54_0.tar.bz2
       URL_MD5 15cb8c0803064faef0c4ddf5bc5ca279
       INSTALL_DIR ${proj}-install
       CONFIGURE_COMMAND "${_boost_cfg_cmd}"
       BUILD_COMMAND "${_boost_build_cmd}"
       INSTALL_COMMAND "${INSTALL_COMMAND}"
       DEPENDS ${proj_DEPENDENCIES}
       )
 
   else()
 
     mitkMacroEmptyExternalProject(${proj} "${proj_DEPENDENCIES}")
 
   endif()
 
 endif()