diff --git a/src/runboat/settings.py b/src/runboat/settings.py
index cae2392..a561838 100644
--- a/src/runboat/settings.py
+++ b/src/runboat/settings.py
@@ -72,11 +72,11 @@ class Settings(BaseSettings):
     ] = None
     # The token to use for the GitHub api calls (to query branches and pull requests,
     # and report build statuses).
-    github_token: str | None
+    github_token: str | None = None
     # The secret used to verify GitHub webhook signatures
-    github_webhook_secret: bytes | None
+    github_webhook_secret: bytes | None = None
     # The file with the python logging configuration to use for the runboat controller.
-    log_config: str | None
+    log_config: str | None = None
     # The base url where the runboat UI and API is exposed on internet.
     # Used to generate backlinks in GitHub statuses
     base_url: str = "http://localhost:8000"