diff --git a/hcloud/core/domain.py b/hcloud/core/domain.py
index d57d52e..1ecf948 100644
--- a/hcloud/core/domain.py
+++ b/hcloud/core/domain.py
@@ -25,10 +25,10 @@ def __repr__(self) -> str:
 
 
 def _make_serializable(value: Any) -> dict | list | str | int | float:
-    if isinstance(value, BoundModelBase):
-        value = value.data_model
+    if isinstance(value, (BaseDomain, BoundModelBase)):
+        if isinstance(value, BoundModelBase):
+            value = value.data_model
 
-    if isinstance(value, BaseDomain):
         return {key: _make_serializable(getattr(value, key)) for key in value.__slots__}
 
     if isinstance(value, dict):