--- a/python/mozbuild/mozbuild/action/exe_7z_archive.py
+++ b/python/mozbuild/mozbuild/action/exe_7z_archive.py
@@ -15,17 +15,17 @@ def archive_exe(pkg_dir, tagfile, sfx_pa
     tmpdir = tempfile.mkdtemp(prefix='tmp')
     subprocess.check_call(['upx', '--best', '-o', mozpath.join(tmpdir, '7zSD.sfx'), sfx_package])
     shutil.move(pkg_dir, 'core')
     subprocess.check_call(['7z', 'a', '-r', '-t7z', mozpath.join(tmpdir, 'app.7z'), '-mx', '-m0=BCJ2', '-m1=LZMA:d25', '-m2=LZMA:d19', '-m3=LZMA:d19', '-mb0:1', '-mb0s1:2', '-mb0s2:3'])
     shutil.move('core', pkg_dir)
     with open(package, 'wb') as o:
         for i in [mozpath.join(tmpdir, '7zSD.sfx'), tagfile, mozpath.join(tmpdir, 'app.7z')]:
             shutil.copyfileobj(open(i, 'rb'), o)
-    os.chmod(package, 755)
+    os.chmod(package, 0755)
 
 def main(args):
     if len(args) != 4:
         print('Usage: exe_7z_archive.py <pkg_dir> <tagfile> <sfx_package> <package>',
               file=sys.stderr)
         return 1
     else:
         archive_exe(args[0], args[1], args[2], args[3])