diff --git a/sklearn/feature_extraction/text.py b/sklearn/feature_extraction/text.py
index e3347f6886432..57ba1cf924b88 100644
--- a/sklearn/feature_extraction/text.py
+++ b/sklearn/feature_extraction/text.py
@@ -586,8 +586,7 @@ def transform(self, X, copy=True):
                 raise ValueError("Input has n_features=%d while the model"
                                  " has been trained with n_features=%d" % (
                                      n_features, expected_n_features))
-            d = sp.lil_matrix((n_features, n_features))
-            d.setdiag(self.idf_)
+            d = sp.dia_matrix((self.idf_, 0), shape=(n_features, n_features))
             # *= doesn't work
             X = X * d