diff --git a/pyner/named_entity/inference.py b/pyner/named_entity/inference.py
index 422a744..3d8ff76 100644
--- a/pyner/named_entity/inference.py
+++ b/pyner/named_entity/inference.py
@@ -1,6 +1,7 @@
 import json
 import logging
 import pathlib
+from typing import Optional
 
 import chainer
 import click
@@ -15,10 +16,10 @@
 
 @click.command()
 @click.argument("model")
-@click.option("--epoch", type=int, required=True)
+@click.option("--epoch", type=int)
 @click.option("--device", type=int, default=-1)
 @click.option("--metric", type=str, default="validation/main/fscore")
-def run_inference(model: str, epoch: int, device: str, metric: str):
+def run_inference(model: str, epoch: Optional[int], device: str, metric: str):
     chainer.config.train = False
 
     if device >= 0:
@@ -29,7 +30,6 @@ def run_inference(model: str, epoch: int, device: str, metric: str):
     model_dir = pathlib.Path(model)
     configs = json.load(open(model_dir / "args"))
 
-    metric = metric.replace("/", ".")
     snapshot_file, prediction_path = select_snapshot(
         epoch, metric, model, model_dir)
     logger.debug(f"creat prediction into {prediction_path}")