diff --git a/modules/icing/pirep_goes.py b/modules/icing/pirep_goes.py
index f8bd1e088fb14d49f53ba43ed6721508205e35af..2a2a1e1532bbd19059c7cfa7e27499bde7fa5b39 100644
--- a/modules/icing/pirep_goes.py
+++ b/modules/icing/pirep_goes.py
@@ -1240,7 +1240,7 @@ def split_data(num_obs, perc=0.2, skip=1):
     np.random.shuffle(test_idxs)
     np.random.shuffle(train_idxs)
 
-    return train_idxs[::skip], test_idxs[::skip]
+    return np.sort(train_idxs[::skip]), np.sort(test_idxs[::skip])
 
 
 def test(filename):