diff --git a/README.md b/README.md
index e18dc52..2408757 100644
--- a/README.md
+++ b/README.md
@@ -35,6 +35,7 @@
 
 - [x] Github Repo 储存支持
 - [ ] Github Release 储存支持
+- [ ] Microsoft Onedrive 储存支持
 - [ ] 基于数据库的用户/权限管理
 - [ ] 操作日志记录
 - [ ] Office Documents 预览支持
diff --git a/storages/factory.py b/storages/factory.py
index b992859..eef33d5 100644
--- a/storages/factory.py
+++ b/storages/factory.py
@@ -29,9 +29,15 @@ class StorageFactory:
         if cls._instance is not None:
             return cls._instance
 
-        storage_type = os.getenv(
-            "STORAGE_TYPE",
-        ).lower()
+        storage_type = os.getenv("STORAGE_TYPE")
+
+        if not storage_type:
+            raise RuntimeError(
+                "STORAGE_TYPE environment variable is not set. "
+                "Supported types: r2, github"
+            )
+
+        storage_type = storage_type.lower()
 
         if storage_type == "r2":
             cls._instance = R2Storage()