diff --git a/tensordict/_td.py b/tensordict/_td.py
index dc1994824..4b5ff73c5 100644
--- a/tensordict/_td.py
+++ b/tensordict/_td.py
@@ -196,33 +196,29 @@ def __init__(
         _is_shared: bool | None = False,
         _is_memmap: bool | None = False,
     ) -> None:
-        self._lock_id = set()
-        self._locked_tensordicts = []
-
         self._is_shared = _is_shared
         self._is_memmap = _is_memmap
         if device is not None and isinstance(device, (int, str)):
             device = torch.device(device)
         self._device = device
 
+        self._tensordict = _tensordict = _StringOnlyDict()
         if not _run_checks:
-            _tensordict: dict = _StringOnlyDict()
             self._batch_size = batch_size
-            for key, value in source.items():
-                if isinstance(value, dict):
-                    value = TensorDict(
-                        value,
-                        batch_size=self._batch_size,
-                        device=self._device,
-                        _run_checks=_run_checks,
-                        _is_shared=_is_shared,
-                        _is_memmap=_is_memmap,
-                    )
-                _tensordict[key] = value
-            self._tensordict = _tensordict
+            if source:  # faster than calling items
+                for key, value in source.items():
+                    if isinstance(value, dict):
+                        value = TensorDict(
+                            value,
+                            batch_size=self._batch_size,
+                            device=self._device,
+                            _run_checks=_run_checks,
+                            _is_shared=_is_shared,
+                            _is_memmap=_is_memmap,
+                        )
+                    _tensordict[key] = value
             self._td_dim_names = names
         else:
-            self._tensordict = _StringOnlyDict()
             if not isinstance(source, (TensorDictBase, dict)):
                 raise ValueError(
                     "A TensorDict source is expected to be a TensorDictBase "
diff --git a/tensordict/base.py b/tensordict/base.py
index 5a467ec60..00646e236 100644
--- a/tensordict/base.py
+++ b/tensordict/base.py
@@ -3758,6 +3758,28 @@ def _propagate_lock(self, lock_ids=None):
         else:
             self._locked_tensordicts += _locked_tensordicts
 
+    @property
+    def _lock_id(self):
+        _lock_id = self.__dict__.get("__lock_id", None)
+        if _lock_id is None:
+            _lock_id = self.__dict__["__lock_id"] = set()
+        return _lock_id
+
+    @_lock_id.setter
+    def _lock_id(self, value):
+        self.__dict__["__lock_id"] = value
+
+    @property
+    def _locked_tensordicts(self):
+        _locked_tensordicts = self.__dict__.get("__locked_tensordicts", None)
+        if _locked_tensordicts is None:
+            _locked_tensordicts = self.__dict__["__locked_tensordicts"] = []
+        return _locked_tensordicts
+
+    @_locked_tensordicts.setter
+    def _locked_tensordicts(self, value):
+        self.__dict__["__locked_tensordicts"] = value
+
     @as_decorator("is_locked")
     def lock_(self) -> T:
         if self.is_locked:
diff --git a/test/test_tensordict.py b/test/test_tensordict.py
index c0893ca9d..4ee3298f1 100644
--- a/test/test_tensordict.py
+++ b/test/test_tensordict.py
@@ -6123,10 +6123,10 @@ def test_empty_tensordict_list_stack(self):
         a0 = td0["a"]
         b0 = td0["a", "b"]
         c0 = td0["a", "b", "c"]
-        assert not hasattr(td, "_locked_tensordicts")
-        assert not hasattr(a, "_locked_tensordicts")
-        assert not hasattr(b, "_locked_tensordicts")
-        assert not hasattr(c, "_locked_tensordicts")
+        assert not td._locked_tensordicts
+        assert not a._locked_tensordicts
+        assert not b._locked_tensordicts
+        assert not c._locked_tensordicts
         assert len(a0._locked_tensordicts)
         assert len(b0._locked_tensordicts)
         td.unlock_()