diff --git a/monkey/monkey_island/cc/services/authentication/json_file_user_datastore.py b/monkey/monkey_island/cc/services/authentication/json_file_user_datastore.py
index 7dd8d82b7..c54489ebd 100644
--- a/monkey/monkey_island/cc/services/authentication/json_file_user_datastore.py
+++ b/monkey/monkey_island/cc/services/authentication/json_file_user_datastore.py
@@ -51,7 +51,7 @@ class JsonFileUserDatastore(IUserDatastore):
             json.dump(self._credentials.to_dict(), f, indent=2)
 
     def get_user_credentials(self, username: str) -> UserCreds:
-        if self._credentials.username != username:
+        if self._credentials is None or self._credentials.username != username:
             raise UnknownUserError(f"User {username} does not exist.")
 
         return self._credentials
diff --git a/monkey/tests/unit_tests/monkey_island/cc/services/test_json_file_user_datastore.py b/monkey/tests/unit_tests/monkey_island/cc/services/test_json_file_user_datastore.py
index 35b342a9f..f3924b8e7 100644
--- a/monkey/tests/unit_tests/monkey_island/cc/services/test_json_file_user_datastore.py
+++ b/monkey/tests/unit_tests/monkey_island/cc/services/test_json_file_user_datastore.py
@@ -75,3 +75,8 @@ def test_get_user_credentials_from_file(tmp_path):
 def test_get_unknown_user(populated_datastore):
     with pytest.raises(UnknownUserError):
         populated_datastore.get_user_credentials("unregistered_user")
+
+
+def test_get_user_credentials__no_user_registered(empty_datastore):
+    with pytest.raises(UnknownUserError):
+        empty_datastore.get_user_credentials("unregistered_user")