diff --git a/sklearn/feature_selection/mutual_info_.py b/sklearn/feature_selection/mutual_info_.py
index d5d1b7fb59db9..7847d3ad752c4 100644
--- a/sklearn/feature_selection/mutual_info_.py
+++ b/sklearn/feature_selection/mutual_info_.py
@@ -247,8 +247,9 @@ def _estimate_mi(X, y, discrete_features='auto', discrete_target=False,
     X, y = check_X_y(X, y, accept_sparse='csc', y_numeric=not discrete_target)
     n_samples, n_features = X.shape
 
-    if discrete_features == 'auto':
-        discrete_features = issparse(X)
+    if type(discrete_features) == str:
+        if discrete_features == 'auto':
+            discrete_features = issparse(X)
 
     if isinstance(discrete_features, bool):
         discrete_mask = np.empty(n_features, dtype=bool)