diff --git a/circle.yml b/circle.yml
index 2110527b..1a9b7f8a 100644
--- a/circle.yml
+++ b/circle.yml
@@ -1,3 +1,6 @@
+machine:
+  post:
+    - pyenv global 2.7.13 3.6.2
 general:
   branches:
     ignore:
@@ -7,6 +10,12 @@ general:
       - master
       - old_master
 test:
-    override:
-        - python -m unittest discover test_replays
-        - python -m unittest discover test_s2gs
+  override:
+    - python2.7 -m flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics
+    - python2.7 -m flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
+    - python2.7 -m python -m unittest discover test_replays
+    - python2.7 -m python -m unittest discover test_s2gs
+    - python3.6 -m flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics
+    - python3.6 -m flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
+    - python3.6 -m python -m unittest discover test_replays
+    - python3.6 -m python -m unittest discover test_s2gs
diff --git a/requirements.txt b/requirements.txt
index 7e2fba5e..4e8c8b6d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1 +1,2 @@
+hacking
 Pillow