diff --git a/tests/apps/python/sub-app/Procfile b/tests/apps/python/sub-app/Procfile
index bb1e3346a..9512e68d7 100644
--- a/tests/apps/python/sub-app/Procfile
+++ b/tests/apps/python/sub-app/Procfile
@@ -1,2 +1,2 @@
 web: python3 web.py
-release: python3 release.py
+release: python3 -u release.py
diff --git a/tests/unit/app-json.bats b/tests/unit/app-json.bats
index 7155f59e9..3ea5fb674 100644
--- a/tests/unit/app-json.bats
+++ b/tests/unit/app-json.bats
@@ -52,7 +52,7 @@ teardown() {
   echo "status: $status"
   assert_success
   assert_output_contains "touch /app/heroku-postdeploy.test"
-  assert_output_contains "python3 release.py"
+  assert_output_contains "python3 -u release.py"
 }
 
 @test "(app-json) app.json scripts missing" {