diff --git a/Lib/test/test_pstats.py b/Lib/test/test_pstats.py
index 095123d..7c28465 100644
--- a/Lib/test/test_pstats.py
+++ b/Lib/test/test_pstats.py
@@ -10,10 +10,16 @@
     def test_combine_results(self):
         """pstats.add_callers should combine the call results of both target
         and source by adding the call time. See issue1269."""
+        # new format: used by the cProfile module
         target = {"a": (1, 2, 3, 4)}
         source = {"a": (1, 2, 3, 4), "b": (5, 6, 7, 8)}
         new_callers = pstats.add_callers(target, source)
         self.assertEqual(new_callers, {'a': (2, 4, 6, 8), 'b': (5, 6, 7, 8)})
+        # old format: used by the profile module
+        target = {"a": 1}
+        source = {"a": 1, "b": 5}
+        new_callers = pstats.add_callers(target, source)
+        self.assertEqual(new_callers, {'a': 2, 'b': 5})
 
 
 def test_main():