diff --git a/b2/_internal/_cli/obj_loads.py b/b2/_internal/_cli/obj_loads.py
index de4a71ae..d7dd3b67 100644
--- a/b2/_internal/_cli/obj_loads.py
+++ b/b2/_internal/_cli/obj_loads.py
@@ -10,6 +10,7 @@
 from __future__ import annotations
 
 import argparse
+import copy
 import io
 import json
 import logging
@@ -53,10 +54,20 @@ def describe_type(type_) -> str:
 _UNDEF = object()
 
 
+def type_with_config(type_: type[T], config: pydantic.ConfigDict) -> type[T]:
+    type_ = copy.copy(type_)
+    if not hasattr(type_, '__config__'):
+        type_.__pydantic_config__ = config
+    else:
+        type_.__config__ = type_.__config__.copy()
+        type_.__config__.update(config)
+    return type_
+
+
 def validated_loads(data: str, expected_type: type[T] | None = None) -> T:
     val = _UNDEF
     if expected_type is not None and pydantic is not None:
-        expected_type = pydantic.with_config(pydantic.ConfigDict(extra="allow"))(expected_type)
+        expected_type = type_with_config(expected_type, pydantic.ConfigDict(extra="allow"))
         try:
             ta = TypeAdapter(expected_type)
         except TypeError: