diff --git a/minetorch/__init__.py b/minetorch/__init__.py
index 23af3a2..068ee94 100644
--- a/minetorch/__init__.py
+++ b/minetorch/__init__.py
@@ -1,6 +1,6 @@
 from .miner import Miner
 from .plugin import Plugin
 
-__version__ = "0.6.15"
+__version__ = "0.6.16"
 
 __all__ = ["Miner", "Plugin"]
diff --git a/minetorch/metrics.py b/minetorch/metrics.py
index c5d31bd..3cdcf2b 100644
--- a/minetorch/metrics.py
+++ b/minetorch/metrics.py
@@ -37,8 +37,8 @@ def before_init(self):
 
     def before_epoch_start(self, epoch):
         self.raw_output = []
-        self.predicts = np.array([]).astype(np.float)
-        self.targets = np.array([]).astype(np.int)
+        self.predicts = []
+        self.targets = []
 
     def after_val_iteration_ended(self, predicts, data, **ignore):
         raw_output = predicts.detach().cpu().numpy()
@@ -47,10 +47,13 @@ def after_val_iteration_ended(self, predicts, data, **ignore):
         targets = data[1].cpu().numpy().reshape([-1])
 
         self.raw_output.append(raw_output)
-        self.predicts = np.concatenate((self.predicts, predicts))
-        self.targets = np.concatenate((self.targets, targets))
+        self.predicts.append(predicts)
+        self.targets.append(targets)
 
     def after_epoch_end(self, val_loss, **ignore):
+        self.predicts = np.concatenate(self.predicts)
+        self.targets = np.concatenate(self.targets)
+
         self._save_results()
         self.accuracy and self._accuracy()
         self.confusion_matrix and self._confusion_matrix()
@@ -119,5 +122,5 @@ def _kappa_score(self):
 
     def _save_results(self):
         file_name = self.plugin_file(f"result.{self.current_epoch}.npz")
-        raw_output = np.stack(self.raw_output)
+        raw_output = np.concatenate(self.raw_output)
         np.savez_compressed(file_name, predicts=self.predicts, targets=self.targets, raw_output=raw_output)
diff --git a/setup.py b/setup.py
index 7f95e0a..aa02d0f 100644
--- a/setup.py
+++ b/setup.py
@@ -6,7 +6,7 @@
 setuptools.setup(
     name='Minetorch',
     description='A tools collection for pytorch users',
-    version='0.6.15',
+    version='0.6.16',
     packages=setuptools.find_packages(),
     include_package_data=True,
     url="https://github.com/minetorch/minetorch",