diff --git a/circle.yml b/circle.yml
index ab69ade37..5d0172d18 100644
--- a/circle.yml
+++ b/circle.yml
@@ -1,4 +1,6 @@
 machine:
+  python:
+    version: 3.5.0
   environment:
     SITL_SPEEDUP: 10
     SITL_RATE: 200