diff --git a/tests/test_issues_mysqlbackend.py b/tests/test_issues_mysqlbackend.py
index 03e5fa37d833c2bcbd8464cd8ea263b3a2d93784..98665a092f0900326a88f201e99e0a2b5c1f1de2 100644
--- a/tests/test_issues_mysqlbackend.py
+++ b/tests/test_issues_mysqlbackend.py
@@ -26,7 +26,6 @@
 import caosdb as db
 from nose import with_setup
 from nose.tools import assert_equal
-import numpy as np
 import pytest
 
 
@@ -71,4 +70,4 @@ def test_issue_18():
 
     C1 = db.Entity(name="C").retrieve()
     pids = [p.id for p in C1.parents]
-    assert_equal(np.unique(pids), len(pids), "Duplicate parents.")
+    assert_equal(len(set(pids)), len(pids), "Duplicate parents.")