diff --git a/torchrl/objectives/ddpg.py b/torchrl/objectives/ddpg.py
index a72b84f69e4..3b4debe6259 100644
--- a/torchrl/objectives/ddpg.py
+++ b/torchrl/objectives/ddpg.py
@@ -200,7 +200,7 @@ def __init__(
         params = TensorDict.from_module(actor_critic)
         params_meta = params.apply(self._make_meta_params, device=torch.device("meta"))
         with params_meta.to_module(actor_critic):
-            self.actor_critic = deepcopy(actor_critic)
+            self.__dict__["actor_critic"] = deepcopy(actor_critic)
 
         self.convert_to_functional(
             actor_network,