diff --git a/data/maker/__init__.py b/data/maker/__init__.py
index 792f18e..3d3788a 100644
--- a/data/maker/__init__.py
+++ b/data/maker/__init__.py
@@ -182,8 +182,8 @@ class Learner(Process):
             
             if self._df[name].size < 5 :
                 continue
-            _index = np.random.choice(np.arange(self._df[name].size),5,False)
-            no_value = [type(value) in [int,float,np.int64,np.int32,np.float32,np.float64] for value in self._df[name].values[_index]]            
+            _index = np.random.choice(np.arange(self._df[name].shape[0]),5,False)
+            no_value = [type(value) in [int,float,np.int64,np.int32,np.float32,np.float64] for value in self._df[name].values[_index] if value is not None]            
             no_value = 0 if np.sum(no_value) > 0 else ''
             try:
                 self._df[name] = self._df[name].fillna(no_value)