diff --git a/AlphaGo/model.py b/AlphaGo/model.py
index e8b5eb9..3cfb900 100644
--- a/AlphaGo/model.py
+++ b/AlphaGo/model.py
@@ -215,9 +215,10 @@ class ResNet(object):
                     self.training_data['states'].append(states)
                     self.training_data['probs'].append(probs)
                     self.training_data['winner'].append(winner)
-                    training_data['states'] = np.concatenate(self.training_data['states'], axis=0)
-                    training_data['probs'] = np.concatenate(self.training_data['probs'], axis=0)
-                    training_data['winner'] = np.concatenate(self.training_data['winner'], axis=0)
+                    if len(self.training_data['states']) == self.window_length:
+                        training_data['states'] = np.concatenate(self.training_data['states'], axis=0)
+                        training_data['probs'] = np.concatenate(self.training_data['probs'], axis=0)
+                        training_data['winner'] = np.concatenate(self.training_data['winner'], axis=0)
 
             if len(self.training_data['states']) != self.window_length:
                 continue