diff --git a/src/borg/testsuite/crypto/crypto_test.py b/src/borg/testsuite/crypto/crypto_test.py
index edaa8b9cfb..6d72b2dbfa 100644
--- a/src/borg/testsuite/crypto/crypto_test.py
+++ b/src/borg/testsuite/crypto/crypto_test.py
@@ -282,7 +282,10 @@ def test_repo_key_detect_does_not_raise_integrity_error(getpass, monkeypatch):
 class TestDeriveKey(BaseTestCase):
     # Create a simple KeyBase subclass with a non-empty crypt_key
     class CustomKey(KeyBase):
+        TYPE = 0x42
+
         def __init__(self, crypt_key, id_key):
+            super().__init__(None)
             self.crypt_key = crypt_key
             self.id_key = id_key