FWIW, if I comment out this code try: from _functools import _lru_cache_wrapper except ImportError: pass in functools.py to use the pure Python version, then I get much larger numbers: $ ./python -m test -R : test_typing Run tests sequentially 0:00:00 [1/1] test_typing beginning 9 repetitions 123456789 ......... test_typing leaked [25003, 25003, 25003, 25003] references, sum=100012 test_typing leaked [9350, 9352, 9352, 9352] memory blocks, sum=37406 test_typing failed