diff --git a/src/bentoml/metrics.py b/src/bentoml/metrics.py
index bc91d85950f..83a7a71c45d 100644
--- a/src/bentoml/metrics.py
+++ b/src/bentoml/metrics.py
@@ -35,6 +35,8 @@ def __call__(self, *args: t.Any, **kwargs: t.Any) -> t.Any:
         return self
 
     def __getattr__(self, item: t.Any) -> t.Any:
+        if item in ("_attr", "_proxy", "_initialized", "_args", "_kwargs"):
+            raise AttributeError(f"Attribute {item} is private to {self}.")
         if self._proxy is None:
             self._load_proxy()
         assert self._initialized