diff --git a/modules/util/viirs_l1b_l2.py b/modules/util/viirs_l1b_l2.py
index 6fc657c17fc59521f79d1dbc10e155d16fe1599f..b4f6676ca12e7a5734ae02ec511713949ea04875 100644
--- a/modules/util/viirs_l1b_l2.py
+++ b/modules/util/viirs_l1b_l2.py
@@ -123,6 +123,8 @@ def run_all(directory, out_directory):
                 data_valid_tiles = []
                 data_train_tiles = []
 
+                num_train_samples = data_train.shape[0]
+                num_valid_samples = data_valid.shape[0]
                 print('   file # done: ', cnt)
                 print('num_train_samples, num_valid_samples: ', num_train_samples, num_valid_samples)
                 total_num_train_samples += num_train_samples
@@ -152,8 +154,8 @@ def run_all(directory, out_directory):
         #np.save(out_directory+'label_train_' + str(cnt), label_train)
         #np.save(out_directory+'label_valid_' + str(cnt), label_valid)
 
-        num_train_samples += data_train.shape[0]
-        num_valid_samples += data_valid.shape[0]
+        num_train_samples = data_train.shape[0]
+        num_valid_samples = data_valid.shape[0]
 
         print('num_train_samples, num_valid_samples: ', num_train_samples, num_valid_samples)
         total_num_train_samples += num_train_samples