diff --git a/Lib/unittest/suite.py b/Lib/unittest/suite.py
index 72b294962b9..a7238522f61 100644
--- a/Lib/unittest/suite.py
+++ b/Lib/unittest/suite.py
@@ -116,7 +116,12 @@ class TestSuite(BaseTestSuite):
         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 465ba75d74d..ab2e16eb99a 100644
--- a/Lib/unittest/test/test_suite.py
+++ b/Lib/unittest/test/test_suite.py
@@ -289,3 +289,16 @@ class Test_TestSuite(unittest.TestCase, TestEquality):
     def test_addTests__string(self):
         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()