diff --git a/torchrl/_utils.py b/torchrl/_utils.py
index f2ce0cf520e..0b4dd03a636 100644
--- a/torchrl/_utils.py
+++ b/torchrl/_utils.py
@@ -117,10 +117,15 @@ def print(prefix=None) -> str:  # noqa: T202
         return "\n".join(string)
 
     @classmethod
-    def todict(cls, percall=True):
+    def todict(cls, percall=True, prefix=None):
+        def _make_key(key):
+            if prefix:
+                return f"{prefix}/{key}"
+            return key
+
         if percall:
-            return {key: val[0] for key, val in cls._REG.items()}
-        return {key: val[1] for key, val in cls._REG.items()}
+            return {_make_key(key): val[0] for key, val in cls._REG.items()}
+        return {_make_key(key): val[1] for key, val in cls._REG.items()}
 
     @staticmethod
     def erase():