diff --git a/setup.py b/setup.py
index 0431f91..4f5fdc0 100644
--- a/setup.py
+++ b/setup.py
@@ -46,7 +46,7 @@ def get_version():
     long_description=readme,
     url="http://maec.mitre.org",
     packages=find_packages(),
-    install_requires=['lxml>=2.2.3', 'cybox>=2.1.0.9,<2.1.1.0'],
+    install_requires=['lxml>=2.2.3', 'cybox>=2.1.0.11,<2.1.1.0'],
     extras_require=extras_require,
     classifiers=[
         "Programming Language :: Python",