diff --git a/backend/tests/unit/test_delete_account_purge_storage.py b/backend/tests/unit/test_delete_account_purge_storage.py
index 4cdefee2c1..e363325849 100644
--- a/backend/tests/unit/test_delete_account_purge_storage.py
+++ b/backend/tests/unit/test_delete_account_purge_storage.py
@@ -48,6 +48,7 @@ def __getattr__(self, name):
     'pusher',
     'modal',
     'ulid',
+    'pytz',
     'twilio',
 )
 
@@ -58,6 +59,16 @@ def _should_stub(name: str) -> bool:
     return any(name == p or name.startswith(p + '.') for p in _STUB_PREFIXES)
 
 
+def _remove_module_tree(prefix: str) -> None:
+    for name in list(sys.modules):
+        if name == prefix or name.startswith(prefix + '.'):
+            sys.modules.pop(name, None)
+
+
+for _prefix in _STUB_PREFIXES:
+    _remove_module_tree(_prefix)
+
+
 class _StubFinder(importlib.abc.MetaPathFinder, importlib.abc.Loader):
     def __init__(self):
         self.created = set()
diff --git a/backend/tests/unit/test_delete_account_stripe_cancel.py b/backend/tests/unit/test_delete_account_stripe_cancel.py
index 4e648142b3..abbf96088d 100644
--- a/backend/tests/unit/test_delete_account_stripe_cancel.py
+++ b/backend/tests/unit/test_delete_account_stripe_cancel.py
@@ -47,6 +47,7 @@ def __getattr__(self, name):
     'pusher',
     'modal',
     'ulid',
+    'pytz',
     'twilio',
 )
 
@@ -57,6 +58,16 @@ def _should_stub(name: str) -> bool:
     return any(name == p or name.startswith(p + '.') for p in _STUB_PREFIXES)
 
 
+def _remove_module_tree(prefix: str) -> None:
+    for name in list(sys.modules):
+        if name == prefix or name.startswith(prefix + '.'):
+            sys.modules.pop(name, None)
+
+
+for _prefix in _STUB_PREFIXES:
+    _remove_module_tree(_prefix)
+
+
 class _StubFinder(importlib.abc.MetaPathFinder, importlib.abc.Loader):
     def __init__(self):
         self.created = set()