diff --git a/mhcflurry/class1_neural_network.py b/mhcflurry/class1_neural_network.py
index 78e7ad69111e072ad2882d6ac66fbcfa0778e6b8..69dd8d6236abf4695c11ed668758a283ad2258fa 100644
--- a/mhcflurry/class1_neural_network.py
+++ b/mhcflurry/class1_neural_network.py
@@ -5,6 +5,7 @@ import weakref
 import itertools
 import os
 import logging
+import random
 import pickle
 
 import numpy
@@ -930,6 +931,7 @@ class Class1NeuralNetwork(object):
                         count,
                         length=length,
                         distribution=aa_distribution))
+            random.shuffle(random_negative_peptides_list)
             random_negative_peptides = EncodableSequences.create(
                 random_negative_peptides_list)
             random_negative_peptides_encoding = (