diff --git a/Lib/test/test_time.py b/Lib/test/test_time.py
index bc5f69e0312..c307bc19baa 100644
--- a/Lib/test/test_time.py
+++ b/Lib/test/test_time.py
@@ -384,7 +384,8 @@ def test_monotonic(self):
         t2 = time.monotonic()
         dt = t2 - t1
         self.assertGreater(t2, t1)
-        self.assertTrue(0.5 <= dt <= 1.0, dt)
+        # Issue #20101: On some Windows machines, dt may be slightly low
+        self.assertTrue(0.45 <= dt <= 1.0, dt)
 
         # monotonic() is a monotonic but non adjustable clock
         info = time.get_clock_info('monotonic')