diff --git a/skopt/learning/forest.py b/skopt/learning/forest.py
index 49c9a3ec..6e663fe9 100644
--- a/skopt/learning/forest.py
+++ b/skopt/learning/forest.py
@@ -196,7 +196,7 @@ class RandomForestRegressor(_sk_RandomForestRegressor):
     """
     def __init__(self, n_estimators=10, criterion='squared_error',
                  max_depth=None, min_samples_split=2, min_samples_leaf=1,
-                 min_weight_fraction_leaf=0.0, max_features='auto',
+                 min_weight_fraction_leaf=0.0, max_features=None,
                  max_leaf_nodes=None, min_impurity_decrease=0.,
                  bootstrap=True, oob_score=False,
                  n_jobs=1, random_state=None, verbose=0, warm_start=False,
@@ -392,7 +392,7 @@ class ExtraTreesRegressor(_sk_ExtraTreesRegressor):
     """
     def __init__(self, n_estimators=10, criterion='squared_error',
                  max_depth=None, min_samples_split=2, min_samples_leaf=1,
-                 min_weight_fraction_leaf=0.0, max_features='auto',
+                 min_weight_fraction_leaf=0.0, max_features=None,
                  max_leaf_nodes=None, min_impurity_decrease=0.,
                  bootstrap=False, oob_score=False,
                  n_jobs=1, random_state=None, verbose=0, warm_start=False,
diff --git a/skopt/learning/tests/test_forest.py b/skopt/learning/tests/test_forest.py
index c6ed610f..00e3b06b 100644
--- a/skopt/learning/tests/test_forest.py
+++ b/skopt/learning/tests/test_forest.py
@@ -39,7 +39,7 @@ def test_random_forest():
                                 max_depth=None, min_samples_split=2,
                                 min_samples_leaf=1,
                                 min_weight_fraction_leaf=0.,
-                                max_features="auto", max_leaf_nodes=None,
+                                max_features=None, max_leaf_nodes=None,
                                 min_impurity_decrease=0., bootstrap=True,
                                 oob_score=False,
                                 n_jobs=1, random_state=1,
@@ -83,7 +83,7 @@ def test_extra_forest():
     clf = ExtraTreesRegressor(n_estimators=10, criterion="squared_error",
                               max_depth=None, min_samples_split=2,
                               min_samples_leaf=1, min_weight_fraction_leaf=0.,
-                              max_features="auto", max_leaf_nodes=None,
+                              max_features=None, max_leaf_nodes=None,
                               min_impurity_decrease=0., bootstrap=False,
                               oob_score=False,
                               n_jobs=1, random_state=1,