diff --git a/setup.py b/setup.py
index f3a4853..1be1b07 100644
--- a/setup.py
+++ b/setup.py
@@ -36,7 +36,7 @@ import sys
 try:
     from setuptools import setup
     kw = {
-        'install_requires': 'pycrypto >= 2.1, < 2.4',
+        'install_requires': 'pycrypto >= 2.1, != 2.4',
     }
 except ImportError:
     from distutils.core import setup