diff --git a/setup.py b/setup.py
index b9186a8..9250e2d 100644
--- a/setup.py
+++ b/setup.py
@@ -283,6 +283,8 @@
     packages=find_packages(where="src", exclude=["_cffi_src", "_cffi_src.*"]),
     include_package_data=True,
 
+    python_requires='>=2.7,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*',
+
     install_requires=[
         "idna >= 2.1",
         "asn1crypto >= 0.21.0",