diff --git a/backend/app/core/config.py b/backend/app/core/config.py
index 804c3f8..a28daad 100644
--- a/backend/app/core/config.py
+++ b/backend/app/core/config.py
@@ -416,6 +416,9 @@ class Settings(BaseSettings):
         )
         env_file_encoding = "utf-8"
         case_sensitive = False
+        # Ignore extra environment variables not defined in Settings
+        # This allows backwards compatibility with old .env files (e.g., Docker)
+        extra = "ignore"
 
     def _resolve_path(self, path_value: str) -> Path:
         """