--- Pillow-4.2.1/mp_compile.py.orig	2017-08-18 16:27:09.000000000 +0100
+++ Pillow-4.2.1/mp_compile.py	2017-08-18 23:34:17.226557000 +0100
@@ -2,7 +2,7 @@
 # Tested on 2.7, looks to be identical to 3.3.
 
 from __future__ import print_function
-from multiprocessing import Pool, cpu_count
+from multiprocessing import Pool, cpu_count, freeze_support
 from distutils.ccompiler import CCompiler
 import os
 import sys
@@ -38,7 +38,9 @@
         output_dir, macros, include_dirs, sources, depends, extra_postargs)
     cc_args = self._get_cc_args(pp_opts, debug, extra_preargs)
 
-    pool = Pool(MAX_PROCS)
+    if __name__ == '__main__':
+        freeze_support()
+        pool = Pool(MAX_PROCS)
     try:
         print("Building using %d processes" % pool._processes)
     except: