diff --git a/requirements.txt b/requirements.txt
index ec869ee16fdd0e6b5ecab0742da1b81f71bf2b87..459e657d6eb7373169a1ccd7dd9e0029c67f77dc 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -68,6 +68,8 @@ defusedxml==0.7.1
     # via -r requirements.in
 distlib==0.3.8
     # via virtualenv
+dnspython==2.6.1
+    # via -r requirements.in
 docutils==0.20.1
     # via
     #   sphinx