diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index 46ad209..8612ec9 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -622,8 +622,13 @@
 
         if not self.support_subsecond(self.fname):
             delta = 1.0
+        elif os.name == 'nt':
+            # On Windows, the usual resolution of time.time() is 15.6 ms.
+            # bpo-30649: Tolerate 50 ms for slow Windows buildbots.
+            delta = 0.050
         else:
-            # On Windows, the usual resolution of time.time() is 15.6 ms
+            # bpo-30649: PPC64 Fedora 3.x buildbot requires
+            # at least a delta of 14 ms
             delta = 0.020
         st = os.stat(self.fname)
         msg = ("st_time=%r, current=%r, dt=%r"