1 files changed, 1 insertions, 0 deletions

diff --git a/tox.ini b/tox.ini
index 5a73bc426..fac659258 100644
--- a/tox.ini
+++ b/tox.ini
@@ -74,6 +74,7 @@ deps =
     check-manifest
 
 [testenv:docs]
+# pin to 3.5 to match what RTD uses
 basepython = python3.5
 whitelist_externals = make
 commands =