diff --git a/python/jiminy_py/src/jiminy_py/tree.py b/python/jiminy_py/src/jiminy_py/tree.py
index 9b33940e8..219029120 100644
--- a/python/jiminy_py/src/jiminy_py/tree.py
+++ b/python/jiminy_py/src/jiminy_py/tree.py
@@ -173,10 +173,20 @@ def _unflatten_as(data: StructNested[Any],
     """
     data_type = type(data)
     if issubclass_mapping(data_type):  # type: ignore[arg-type]
-        return data_type({  # type: ignore[call-arg]
-            key: _unflatten_as(value, data_leaf_it)
+        flat_items = [
+            (key, _unflatten_as(value, data_leaf_it))
             for key, value in data.items()  # type: ignore[union-attr]
-        })
+        ]
+        try:
+            # Initialisation from dict cannot be the default path as
+            # `gym.spaces.Dict` would sort keys in this specific scenario,
+            # which must be avoided.
+            return data_type(flat_items)  # type: ignore[call-arg]
+        except (ValueError, RuntimeError):
+            # Fallback to initialisation from dict in the rare event of
+            # a container type not supporting initialisation from a
+            # sequence of key-value pairs.
+            return data_type(dict(flat_items))  # type: ignore[call-arg]
     if issubclass_sequence(data_type):  # type: ignore[arg-type]
         return data_type(tuple(  # type: ignore[call-arg]
             _unflatten_as(value, data_leaf_it) for value in data