diff --git a/alternator-test/test_expected.py b/alternator-test/test_expected.py
index a48084fe7f..5febcf9402 100644
--- a/alternator-test/test_expected.py
+++ b/alternator-test/test_expected.py
@@ -82,6 +82,29 @@ def test_update_expected_1_eq_true(test_table_s):
                             'AttributeValueList': [2, 3]}}
         )
 
+# Check that set equality is checked correctly. Unlike string equality (for
+# example), it cannot be done with just naive string comparison of the JSON
+# representation, and we need to allow for any order.
+@pytest.mark.xfail(reason="bug in EQ test of sets")
+def test_update_expected_1_eq_set(test_table_s):
+    p = random_string()
+    # Because boto3 sorts the set values we give it, in order to generate a
+    # set with a different order, we need to build it incrementally.
+    test_table_s.update_item(Key={'p': p},
+        AttributeUpdates={'a': {'Value': set(['dog', 'chinchilla']), 'Action': 'PUT'}})
+    test_table_s.update_item(Key={'p': p},
+        UpdateExpression='ADD a :val1',
+        ExpressionAttributeValues={':val1': set(['cat', 'mouse'])})
+    # Sanity check - the attribute contains the set we think it does
+    assert test_table_s.get_item(Key={'p': p}, ConsistentRead=True)['Item']['a'] == set(['chinchilla', 'cat', 'dog', 'mouse'])
+    # Now finally check that "Expected"'s equality check knows the equality too.
+    test_table_s.update_item(Key={'p': p},
+        AttributeUpdates={'b': {'Value': 3, 'Action': 'PUT'}},
+        Expected={'a': {'ComparisonOperator': 'EQ',
+                        'AttributeValueList': [set(['chinchilla', 'cat', 'dog', 'mouse'])]}}
+    )
+    assert 'b' in test_table_s.get_item(Key={'p': p}, ConsistentRead=True)['Item']
+
 def test_update_expected_1_eq_false(test_table_s):
     p = random_string()
     test_table_s.update_item(Key={'p': p},