diff --git a/CMake/FindNumpy.cmake b/CMake/FindNumpy.cmake
index 4170adb613..8e798cc8f8 100644
--- a/CMake/FindNumpy.cmake
+++ b/CMake/FindNumpy.cmake
@@ -1,29 +1,35 @@
 #  Variables set by this script
 #  NUMPY_FOUND
 #  NUMPY_INCLUDE_DIR
 
 find_package(PackageHandleStandardArgs)
 
 # numpy dir defined, own numpy deployed in python runtime
 if(DEFINED Numpy_DIR AND EXISTS ${Numpy_DIR})
   if(EXISTS ${Numpy_DIR}/core/include)
     set(NUMPY_INCLUDE_DIR  ${Numpy_DIR}/core/include)
   endif()
 else() #numpy dir not defined
+
+  set(_python ${PYTHON_EXECUTABLE})
+  if(UNIX)
+    STRING(REPLACE " " "\ " _python ${PYTHON_EXECUTABLE})
+  endif()
+
   execute_process (
-     COMMAND ${PYTHON_EXECUTABLE} -c "import os; os.environ['DISTUTILS_USE_SDK']='1'; import numpy.distutils; print numpy.distutils.misc_util.get_numpy_include_dirs()[0]"
+     COMMAND ${_python} -c "import os; os.environ['DISTUTILS_USE_SDK']='1'; import numpy.distutils; print numpy.distutils.misc_util.get_numpy_include_dirs()[0]"
      OUTPUT_VARIABLE output
      OUTPUT_STRIP_TRAILING_WHITESPACE
   )
 
   if(DEFINED output AND EXISTS ${output} )
     set (NUMPY_INCLUDE_DIR ${output})
   endif()
 endif()
 
 FIND_PACKAGE_HANDLE_STANDARD_ARGS(Numpy DEFAULT_MSG NUMPY_INCLUDE_DIR)
 
 MARK_AS_ADVANCED (
   NUMPY_INCLUDE_DIR
 )
 
diff --git a/CMake/mitkFunctionExternalPythonBuildStep.cmake b/CMake/mitkFunctionExternalPythonBuildStep.cmake
index 0a6f55570d..ad1e3b219f 100644
--- a/CMake/mitkFunctionExternalPythonBuildStep.cmake
+++ b/CMake/mitkFunctionExternalPythonBuildStep.cmake
@@ -1,39 +1,49 @@
 #! CMake function that runs a python build step from a setup.py script,
 #! e.g. python setup.py build. This is used to build external python
 #! libraries like numpy. The function takes the necessary build steps,
 #! python executable etc. as arguments. The specific build command executed
 #! by the runtime is passed as ARGN.
 #!
 #! params:
 #!  proj - The name of the project
 #!  step - Buildstep used to label the generated outputs, e.g. configure;build;install
 #!  _python_executable - The python executable
 #!  _bin_dir - The current binary from where commands are executed relative to it
 #!  ARGN - Python command that will be run in the _bin_dir/proj-src folder
 #!         e.g. setup.py build --someflags
 #!
 function(mitkFunctionExternalPythonBuildStep proj step _python_executable _bin_dir)
 
   # the specific python build command run by this step
   set(_command ${ARGN})
 
-  message("Running ${proj} ${step}:${PYTHON_EXECUTABLE} ${_command}")
+  message("Running ${proj} ${step}:${_python_executable} ${_command}")
+
+  set(_workdir ${_bin_dir}/${proj}-src)
+  set(_prefixdir ${_bin_dir}/${proj}-cmake)
+  set(_python ${_python_executable})
+  # escape spaces
+  if(UNIX)
+    STRING(REPLACE " " "\ " _workdir ${_workdir})
+    STRING(REPLACE " " "\ " _prefixdir ${_prefixdir})
+    STRING(REPLACE " " "\ " _python ${_python})
+  endif()
 
   execute_process(
-     COMMAND ${_python_executable} ${_command}
-     WORKING_DIRECTORY ${_bin_dir}/${proj}-src
+     COMMAND ${_python} ${_command}
+     WORKING_DIRECTORY ${_workdir}
      RESULT_VARIABLE result
      OUTPUT_VARIABLE output
      ERROR_VARIABLE error
   )
-  set(output_file "${_bin_dir}/${proj}-cmake/${proj}_${step}_step_output.txt")
+  set(output_file "${_prefixdir}/${proj}_${step}_step_output.txt")
   file(WRITE ${output_file} ${output})
 
-  set(error_file "${_bin_dir}/${proj}-cmake/${proj}_${step}_step_error.txt")
+  set(error_file "${_prefixdir}/${proj}_${step}_step_error.txt")
   file(WRITE ${error_file} ${error})
 
   if(NOT ${result} EQUAL 0)
     message(FATAL_ERROR "Error in: ${proj}: ${error}")
   endif()
 endfunction()
 
diff --git a/CMakeExternals/Numpy.cmake b/CMakeExternals/Numpy.cmake
index 9ebcedd385..171fc41833 100644
--- a/CMakeExternals/Numpy.cmake
+++ b/CMakeExternals/Numpy.cmake
@@ -1,91 +1,98 @@
 #-----------------------------------------------------------------------------
 # Numpy
 #-----------------------------------------------------------------------------
 if( MITK_USE_Python AND NOT MITK_USE_SYSTEM_PYTHON )
   # Sanity checks
   if(DEFINED Numpy_DIR AND NOT EXISTS ${Numpy_DIR})
     message(FATAL_ERROR "Numpy_DIR variable is defined but corresponds to non-existing directory")
   endif()
 
   if( NOT DEFINED Numpy_DIR )
     set(proj Numpy)
     set(${proj}_DEPENDENCIES Python)
     set(Numpy_DEPENDS ${proj})
 
     # setup build environment and disable fortran, blas and lapack
     set(_numpy_env
         "
         set(ENV{F77} \"\")
         set(ENV{F90} \"\")
         set(ENV{FFLAGS} \"\")
         set(ENV{ATLAS} \"None\")
         set(ENV{BLAS} \"None\")
         set(ENV{LAPACK} \"None\")
         set(ENV{MKL} \"None\")
         set(ENV{VS_UNICODE_OUTPUT} \"\")
         set(ENV{CC} \"${CMAKE_C_COMPILER} ${CMAKE_C_COMPILER_ARG1}\")
         set(ENV{CFLAGS} \"${CMAKE_C_FLAGS} ${CMAKE_C_FLAGS_RELEASE}\")
         set(ENV{CXX} \"${CMAKE_CXX_COMPILER} ${CMAKE_CXX_COMPILER_ARG1}\")
         set(ENV{CXXFLAGS} \"${CMAKE_CXX_FLAGS} ${CMAKE_CXX_FLAGS_RELEASE}\")
         set(ENV{LDFLAGS} \"${CMAKE_LINKER_FLAGS} ${CMAKE_LINKER_FLAGS_RELEASE}\")
 
         ")
 
     set(_numpy_build_step ${MITK_SOURCE_DIR}/CMake/mitkFunctionExternalPythonBuildStep.cmake)
 
     set(_configure_step ${CMAKE_BINARY_DIR}/${proj}-cmake/${proj}_configure_step.cmake)
     file(WRITE ${_configure_step}
        "${_numpy_env}
         include(\"${_numpy_build_step}\")
         file(WRITE \"${CMAKE_BINARY_DIR}/${proj}-src/site.cfg\" \"\")
-        mitkFunctionExternalPythonBuildStep(${proj} configure ${PYTHON_EXECUTABLE} \"${CMAKE_BINARY_DIR}\" setup.py config)
+        mitkFunctionExternalPythonBuildStep(${proj} configure \"${PYTHON_EXECUTABLE}\" \"${CMAKE_BINARY_DIR}\" setup.py config)
        ")
 
     # build step
     set(_build_step ${CMAKE_BINARY_DIR}/${proj}-cmake/${proj}_build_step.cmake)
     file(WRITE ${_build_step}
        "${_numpy_env}
         include(\"${_numpy_build_step}\")
-        mitkFunctionExternalPythonBuildStep(${proj} build ${PYTHON_EXECUTABLE} \"${CMAKE_BINARY_DIR}\" setup.py build --fcompiler=none)
+        mitkFunctionExternalPythonBuildStep(${proj} build \"${PYTHON_EXECUTABLE}\" \"${CMAKE_BINARY_DIR}\" setup.py build --fcompiler=none)
        ")
 
     # install step
-    set(_install_dir ${Python_DIR})
+    set(_install_dir "${Python_DIR}")
     if(WIN32)
       STRING(REPLACE "/" "\\\\" _install_dir ${Python_DIR})
     else()
       # escape scpaces on unix
       STRING(REPLACE " " "\ " _install_dir ${Python_DIR})
     endif()
 
     set(_install_step ${CMAKE_BINARY_DIR}/${proj}-cmake/${proj}_install_step.cmake)
     file(WRITE ${_install_step}
        "${_numpy_env}
         include(\"${_numpy_build_step}\")
-        mitkFunctionExternalPythonBuildStep(${proj} install ${PYTHON_EXECUTABLE} \"${CMAKE_BINARY_DIR}\" setup.py install --prefix=${_install_dir})
+        mitkFunctionExternalPythonBuildStep(${proj} install \"${PYTHON_EXECUTABLE}\" \"${CMAKE_BINARY_DIR}\" setup.py install --prefix=\"${_install_dir}\")
        ")
 
     set(Numpy_URL ${MITK_THIRDPARTY_DOWNLOAD_PREFIX_URL}/numpy-1.4.1.tar.gz)
     set(Numpy_MD5 "5c7b5349dc3161763f7f366ceb96516b")
 
+    # escape spaces
+    if(UNIX)
+      STRING(REPLACE " " "\ " _configure_step ${_configure_step})
+      STRING(REPLACE " " "\ " _build_step ${_build_step})
+      STRING(REPLACE " " "\ " _install_step ${_install_step})
+    endif()
+
     ExternalProject_Add(${proj}
       URL ${Numpy_URL}
       URL_MD5 ${Numpy_MD5}
       SOURCE_DIR ${proj}-src
       PREFIX ${proj}-cmake
       BUILD_IN_SOURCE 1
       CONFIGURE_COMMAND ${CMAKE_COMMAND} -P ${_configure_step}
       BUILD_COMMAND   ${CMAKE_COMMAND} -P ${_build_step}
       INSTALL_COMMAND ${CMAKE_COMMAND} -P ${_install_step}
 
       DEPENDS
         ${${proj}_DEPENDENCIES}
     )
 
     set(Numpy_DIR ${MITK_PYTHON_SITE_DIR}/numpy)
 
   else()
     mitkMacroEmptyExternalProject(${proj} "${proj_DEPENDENCIES}")
   endif()
 endif()