diff --git a/setup.py b/setup.py
index de59ec9a..6dd2cad7 100755
--- a/setup.py
+++ b/setup.py
@@ -40,7 +40,8 @@ packages = ['requests']
 requires = [
     'chardet>=3.0.2,<3.1.0',
     'idna>=2.5,<2.6',
-    'urllib3 >=1.21.1,<1.22'
+    'urllib3>=1.21.1,<1.22',
+    'certifi>=2017.4.17'
 
 ]
 test_requirements = ['pytest>=2.8.0', 'pytest-httpbin==0.0.7', 'pytest-cov', 'pytest-mock']