diff --git a/tests/hazmat/primitives/test_aead.py b/tests/hazmat/primitives/test_aead.py
index d129a98ebc58..635a8029eaf1 100644
--- a/tests/hazmat/primitives/test_aead.py
+++ b/tests/hazmat/primitives/test_aead.py
@@ -39,7 +39,11 @@ def _aead_supported(cls):
 
 def large_mmap(length: int = 2**32):
     # Silencing mypy warning on Windows, even though mmap doesn't exist there.
-    return mmap.mmap(-1, length, prot=mmap.PROT_READ)  # type: ignore
+    # See: https://mypy.readthedocs.io/en/stable/common_issues.html#version-and-platform-checks
+    if sys.platform != "win32":
+        return mmap.mmap(-1, length, prot=mmap.PROT_READ)
+    else:
+        return mmap.mmap(-1, length)  # pragma: no cover
 
 
 @pytest.mark.skipif(