diff -up ./setup.py.orig ./setup.py
--- ./setup.py.orig	2018-10-15 20:43:34.000000000 +0200
+++ ./setup.py	2018-11-01 15:56:18.995147704 +0100
@@ -25,6 +25,20 @@
 # --------------------------------------------------------------------------
 
 from setuptools import setup, find_packages
+import sys
+
+install_requires = [
+    "requests>=2.16,<2.17",
+    "requests_oauthlib>=0.5.0",
+    "isodate>=0.6.0",
+    "certifi>=2017.4.17"
+]
+if sys.version_info < (3, 4):
+    install_requires.append("enum34>=1.0.4")
+if sys.version_info < (3, 5):
+    install_requires.append("typing")
+else:
+    install_requires += ["aiohttp>=3.0", "aiodns"]
 
 setup(
     name='msrest',
@@ -47,18 +61,5 @@ setup(
         'Programming Language :: Python :: 3.7',
         'License :: OSI Approved :: MIT License',
         'Topic :: Software Development'],
-    install_requires=[
-        "requests~=2.16",
-        "requests_oauthlib>=0.5.0",
-        "isodate>=0.6.0",
-        "certifi>=2017.4.17",
-    ],
-    extras_require={
-        ":python_version<'3.4'": ['enum34>=1.0.4'],
-        ":python_version<'3.5'": ['typing'],
-        "async:python_version>='3.5'": [
-            'aiohttp>=3.0',
-            'aiodns'
-        ],
-    }
+    install_requires=install_requires
 )