diff --git a/tools/test_runner.py b/tools/test_runner.py
index 1979ce01e4..2121907e33 100755
--- a/tools/test_runner.py
+++ b/tools/test_runner.py
@@ -170,7 +170,7 @@ def collect(targets, keyword):
       cls = type(test)
       if cls.__name__ == "_FailedTest":
         continue
-      if getattr(cls, "__unittest_skip_why__", "") == "parameterized base class":
+      if cls.__dict__.get("__unittest_skip_why__", "") == "parameterized base class":
         continue
       if not keyword or keyword.lower() in test.id().lower():
         tests.append(test)