diff --git a/run_tests.py b/run_tests.py
index 79a05a5..3ee8091 100644
--- a/run_tests.py
+++ b/run_tests.py
@@ -579,4 +579,5 @@ def test_builtin_works_on_many_examples(source_code):
             raise
         tree = ast.parse(source)
         checker = BuiltinsChecker(tree, '/home/script.py')
-        assert isinstance([c for c in checker.run()], list)
+        for c in checker.run():
+            assert isinstance(c, list)