diff --git a/Lib/unittest/suite.py b/Lib/unittest/suite.py
index 0dd2dc5..cf6d94a 100644
--- a/Lib/unittest/suite.py
+++ b/Lib/unittest/suite.py
@@ -119,7 +119,12 @@
         if getattr(currentClass, "__unittest_skip__", False):
             return
 
-        currentClass._classSetupFailed = False
+        try:
+            currentClass._classSetupFailed = False
+        except TypeError:
+            # test may actually be a function
+            # so its class will be a builtin-type
+            pass
 
         setUpClass = getattr(currentClass, 'setUpClass', None)
         if setUpClass is not None:
diff --git a/Lib/unittest/test/test_suite.py b/Lib/unittest/test/test_suite.py
index 7cd2b89..2b8d678 100644
--- a/Lib/unittest/test/test_suite.py
+++ b/Lib/unittest/test/test_suite.py
@@ -290,6 +290,15 @@
         suite = unittest.TestSuite()
         self.assertRaises(TypeError, suite.addTests, "foo")
 
+    def test_function_in_suite(self):
+        def f(_):
+            pass
+        suite = unittest.TestSuite()
+        suite.addTest(f)
+
+        # when the bug is fixed this line will not crash
+        suite.run(unittest.TestResult())
+
 
 if __name__ == '__main__':
     unittest.main()