diff --git a/src/runboat/settings.py b/src/runboat/settings.py
index 7c796ab..0439a37 100644
--- a/src/runboat/settings.py
+++ b/src/runboat/settings.py
@@ -1,6 +1,6 @@
 from typing import Optional
 
-from pydantic import BaseSettings
+from pydantic import BaseSettings, validator
 
 
 class Settings(BaseSettings):
@@ -24,5 +24,10 @@ class Settings(BaseSettings):
     class Config:
         env_prefix = "RUNBOAT_"
 
+    @validator("supported_repos")
+    @classmethod
+    def validate_supported_repos(v) -> set[str]:
+        return {item.lower() for item in v}
+
 
 settings = Settings()