diff --git a/metric_learn/constraints.py b/metric_learn/constraints.py
index ce71ecd2..903c5148 100644
--- a/metric_learn/constraints.py
+++ b/metric_learn/constraints.py
@@ -3,7 +3,6 @@
 from supervised data labels.
 """
 import numpy as np
-import random
 import warnings
 from six.moves import xrange
 from scipy.sparse import coo_matrix