diff --git a/.circleci/config.yml b/.circleci/config.yml
index 7c350501..1d0a2954 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -14,6 +14,9 @@ jobs:
       - run:
           name: Run tests and collect coverage
           command: pytest --cov app
+      - run:
+          name: set -u
+          command: set -u
       - codecov/upload
 
 workflow: