diff --git a/setup.py b/setup.py
index 42b0479..066027a 100755
--- a/setup.py
+++ b/setup.py
@@ -30,5 +30,5 @@ setup(name='rfc3161',
         author='Benjamin Dauvergne',
         author_email='bdauvergne@entrouvert.com',
         packages=['rfc3161'],
-        requires=['pyasn1'],
+        requires=['pyasn1', 'pyasn1_modules', 'M2Crypto'],
         cmdclass={'test': TestCommand})