--- a/python/virtualenv/virtualenv.py
+++ b/python/virtualenv/virtualenv.py
@@ -1125,17 +1125,23 @@ def install_python(home_dir, lib_dir, in
     import site
     site_filename = site.__file__
     if site_filename.endswith('.pyc') or site_filename.endswith('.pyo'):
         site_filename = site_filename[:-1]
     elif site_filename.endswith('$py.class'):
         site_filename = site_filename.replace('$py.class', '.py')
     site_filename_dst = change_prefix(site_filename, home_dir)
     site_dir = os.path.dirname(site_filename_dst)
-    writefile(site_filename_dst, SITE_PY)
+    # MOZ: Copies a site.py if it exists instead of using the one hex encoded in
+    # this file. Necessary for some site.py fixes for MinGW64 version of python
+    site_py_src_path = os.path.join(os.path.dirname(__file__), 'site.py')
+    if os.path.isfile(site_py_src_path):
+        shutil.copy(site_py_src_path, site_filename_dst)
+    else:
+        writefile(site_filename_dst, SITE_PY)
     writefile(join(site_dir, 'orig-prefix.txt'), prefix)
     site_packages_filename = join(site_dir, 'no-global-site-packages.txt')
     if not site_packages:
         writefile(site_packages_filename, '')
 
     if is_pypy or is_win:
         stdinc_dir = join(prefix, 'include')
     else: