diff --git a/pymispwarninglists/api.py b/pymispwarninglists/api.py
index 0c21d77..c80ea3c 100644
--- a/pymispwarninglists/api.py
+++ b/pymispwarninglists/api.py
@@ -33,6 +33,7 @@ class WarningList():
     def __init__(self, warninglist: Dict[str, Any], slow_search: bool=False):
         self.warninglist = warninglist
         self.list = self.warninglist['list']
+        self.set = set(self.list)
         self.description = self.warninglist['description']
         self.version = int(self.warninglist['version'])
         self.name = self.warninglist['name']
@@ -71,7 +72,7 @@ class WarningList():
         return json.dumps(self, default=json_default)
 
     def _fast_search(self, value) -> bool:
-        return value in self.list
+        return value in self.set
 
     def _network_index(self) -> List:
         to_return = []
diff --git a/tests/tests.py b/tests/tests.py
index 16bfc95..90b77ad 100644
--- a/tests/tests.py
+++ b/tests/tests.py
@@ -39,7 +39,7 @@ class TestPyMISPWarningLists(unittest.TestCase):
     def test_slow_search(self):
         self.warninglists = WarningLists(True)
         results = self.warninglists.search('8.8.8.8')
-        self.assertEqual(results[0].name, 'List of known IPv4 public DNS resolvers')
+        self.assertIn('List of known IPv4 public DNS resolvers', [r.name for r in results])
         results = self.warninglists.search('100.64.1.56')
         self.assertEqual(results[0].name, 'List of RFC 6598 CIDR blocks')
         results = self.warninglists.search('2001:DB8::34:1')