diff --git a/python-package/xgboost/training.py b/python-package/xgboost/training.py
index af9d6541d..03e24bdba 100644
--- a/python-package/xgboost/training.py
+++ b/python-package/xgboost/training.py
@@ -63,7 +63,7 @@ def train(params, dtrain, num_boost_round=10, evals=(), obj=None, feval=None,
     evals = list(evals)
     ntrees = 0
     if xgb_model is not None:
-        if xgb_model is not isinstance(xgb_model, STRING_TYPES):
+        if not isinstance(xgb_model, STRING_TYPES):
             xgb_model = xgb_model.save_raw()
         bst = Booster(params, [dtrain] + [d[0] for d in evals], model_file=xgb_model)
         ntrees = len(bst.get_dump())