diff --git a/.travis.yml b/.travis.yml
index 5bbc668..cc539ad 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,6 +4,6 @@ python:
   - "3.6"
 
 # command to install dependencies
-install: pip install pipenv; pipenv install --dev
+install: pip install pipenv; pipenv lock; pipenv install --dev
 # command to run tests
 script: pipenv run pytest