diff --git a/python-package/xgboost/core.py b/python-package/xgboost/core.py
index 7f1ad1727922..47e05b614220 100644
--- a/python-package/xgboost/core.py
+++ b/python-package/xgboost/core.py
@@ -1175,6 +1175,11 @@ def save_model(self, fname):
         """
         Save the model to a file.
 
+        The model is saved in an XGBoost internal binary format which is
+        universal among the various XGBoost interfaces. Auxiliary attributes of
+        the Python Booster object (such as feature_names) will not be saved.
+        To preserve all attributes, pickle the Booster object.
+
         Parameters
         ----------
         fname : string
@@ -1204,6 +1209,11 @@ def load_model(self, fname):
         """
         Load the model from a file.
 
+        The model is loaded from an XGBoost internal binary format which is
+        universal among the various XGBoost interfaces. Auxiliary attributes of
+        the Python Booster object (such as feature_names) will not be loaded.
+        To preserve all attributes, pickle the Booster object.
+
         Parameters
         ----------
         fname : string or a memory buffer