Explicitly declare Python 3.8 as supported
diff --git a/setup.py b/setup.py
index 8693427..a10bfbe 100755
--- a/setup.py
+++ b/setup.py
@@ -48,10 +48,12 @@
               'Programming Language :: Python :: 3.5',
               'Programming Language :: Python :: 3.6',
               'Programming Language :: Python :: 3.7',
+              'Programming Language :: Python :: 3.8',
               'Programming Language :: Python :: Implementation :: CPython',
               'Programming Language :: Python :: Implementation :: PyPy',
               'Topic :: Security :: Cryptography',
           ],
+          python_requires='>=3.5, <4',
           install_requires=[
               'pyasn1 >= 0.1.3',
           ],