diff --git a/app.json b/app.json
index 737e5eb0..1970942c 100644
--- a/app.json
+++ b/app.json
@@ -4,6 +4,7 @@
   "scripts": {
     "postdeploy": "python manage.py migrate && python manage.py generateSampleData"
   },
+  "stack": "heroku-18",
   "env": {
     "DEBUG": {
       "required": true