diff --git a/sqlalchemy_rdsiam/rds.py b/sqlalchemy_rdsiam/rds.py
index 58d0c57..4f4547b 100644
--- a/sqlalchemy_rdsiam/rds.py
+++ b/sqlalchemy_rdsiam/rds.py
@@ -21,6 +21,6 @@
 import boto3
 
 
-@functools.lru_cache
+@functools.lru_cache()
 def rds_client(region_name: str) -> Any:
     return boto3.client("rds", region_name=region_name)