diff --git a/src/_zkapauthorizer/tests/test_storage_protocol.py b/src/_zkapauthorizer/tests/test_storage_protocol.py
index 7d9de02808dde0a547ded59ad4cd3592ff5fdcb1..ee0dc5ba671e36fa5a2c4b3e8e039ea5d731568e 100644
--- a/src/_zkapauthorizer/tests/test_storage_protocol.py
+++ b/src/_zkapauthorizer/tests/test_storage_protocol.py
@@ -23,6 +23,9 @@ from __future__ import (
 from fixtures import (
     MonkeyPatch,
 )
+from unittest import (
+    skipIf,
+)
 from testtools import (
     TestCase,
 )
@@ -54,6 +57,9 @@ from hypothesis.strategies import (
     integers,
 )
 
+from twisted.python.runtime import (
+    platform,
+)
 from twisted.python.filepath import (
     FilePath,
 )
@@ -395,6 +401,7 @@ class ShareTests(TestCase):
         )
 
 
+    @skipIf(platform.isWindows(), "Storage server miscomputes slot size on Windows")
     @given(
         storage_index=storage_indexes(),
         secrets=tuples(
diff --git a/src/_zkapauthorizer/tests/test_storage_server.py b/src/_zkapauthorizer/tests/test_storage_server.py
index 482b2e942b35904f95434efbe9f4b095097b5540..40500cb142581eff203eeb0d002ac1cd8e013fb6 100644
--- a/src/_zkapauthorizer/tests/test_storage_server.py
+++ b/src/_zkapauthorizer/tests/test_storage_server.py
@@ -104,11 +104,11 @@ from ..storage_common import (
     summarize,
 )
 
-@skipIf(platform.isWindows(), "Storage server is not supported on Windows")
 class PassValidationTests(TestCase):
     """
     Tests for pass validation performed by ``ZKAPAuthorizerStorageServer``.
     """
+    @skipIf(platform.isWindows(), "Storage server is not supported on Windows")
     def setUp(self):
         super(PassValidationTests, self).setUp()
         self.clock = Clock()