diff --git a/fastapi/dependencies/utils.py b/fastapi/dependencies/utils.py
index c9f618132..a1bfe2bb1 100644
--- a/fastapi/dependencies/utils.py
+++ b/fastapi/dependencies/utils.py
@@ -22,8 +22,8 @@ from fastapi.dependencies.models import Dependant, SecurityRequirement
 from fastapi.security.base import SecurityBase
 from fastapi.security.oauth2 import OAuth2, SecurityScopes
 from fastapi.security.open_id_connect_url import OpenIdConnect
-from fastapi.utils import UnconstrainedConfig, get_path_param_names
-from pydantic import Schema, create_model
+from fastapi.utils import get_path_param_names
+from pydantic import BaseConfig, Schema, create_model
 from pydantic.error_wrappers import ErrorWrapper
 from pydantic.errors import MissingError
 from pydantic.fields import Field, Required, Shape
@@ -203,8 +203,8 @@ def add_param_to_fields(
         default=None if required else default_value,
         alias=alias,
         required=required,
-        model_config=UnconstrainedConfig,
-        class_validators=[],
+        model_config=BaseConfig,
+        class_validators={},
         schema=schema,
     )
     if schema.in_ == params.ParamTypes.path:
@@ -237,8 +237,8 @@ def add_param_to_body_fields(*, param: inspect.Parameter, dependant: Dependant)
         default=None if required else default_value,
         alias=schema.alias or param.name,
         required=required,
-        model_config=UnconstrainedConfig,
-        class_validators=[],
+        model_config=BaseConfig,
+        class_validators={},
         schema=schema,
     )
     dependant.body_params.append(field)
@@ -336,7 +336,7 @@ def request_params_to_args(
                     ErrorWrapper(
                         MissingError(),
                         loc=(schema.in_.value, field.alias),
-                        config=UnconstrainedConfig,
+                        config=BaseConfig,
                     )
                 )
             else:
@@ -379,9 +379,7 @@ async def request_body_to_args(
                 if field.required:
                     errors.append(
                         ErrorWrapper(
-                            MissingError(),
-                            loc=("body", field.alias),
-                            config=UnconstrainedConfig,
+                            MissingError(), loc=("body", field.alias), config=BaseConfig
                         )
                     )
                 else:
@@ -456,8 +454,8 @@ def get_body_field(*, dependant: Dependant, name: str) -> Optional[Field]:
         type_=BodyModel,
         default=None,
         required=required,
-        model_config=UnconstrainedConfig,
-        class_validators=[],
+        model_config=BaseConfig,
+        class_validators={},
         alias="body",
         schema=BodySchema(None),
     )
diff --git a/fastapi/routing.py b/fastapi/routing.py
index fe0ff6c2c..4fe622c02 100644
--- a/fastapi/routing.py
+++ b/fastapi/routing.py
@@ -7,8 +7,7 @@ from fastapi import params
 from fastapi.dependencies.models import Dependant
 from fastapi.dependencies.utils import get_body_field, get_dependant, solve_dependencies
 from fastapi.encoders import jsonable_encoder
-from fastapi.utils import UnconstrainedConfig
-from pydantic import BaseModel, Schema
+from pydantic import BaseConfig, BaseModel, Schema
 from pydantic.error_wrappers import ErrorWrapper, ValidationError
 from pydantic.fields import Field
 from pydantic.utils import lenient_issubclass
@@ -59,7 +58,7 @@ def get_app(
                     if body_bytes:
                         body = await request.json()
         except Exception as e:
-            logging.error("Error getting request body", e)
+            logging.error(f"Error getting request body: {e}")
             raise HTTPException(
                 status_code=400, detail="There was an error parsing the body"
             )
@@ -126,10 +125,10 @@ class APIRoute(routing.Route):
             self.response_field: Optional[Field] = Field(
                 name=response_name,
                 type_=self.response_model,
-                class_validators=[],
+                class_validators={},
                 default=None,
                 required=False,
-                model_config=UnconstrainedConfig,
+                model_config=BaseConfig,
                 schema=Schema(None),
             )
         else:
@@ -155,7 +154,7 @@ class APIRoute(routing.Route):
                     class_validators=None,
                     default=None,
                     required=False,
-                    model_config=UnconstrainedConfig,
+                    model_config=BaseConfig,
                     schema=Schema(None),
                 )
                 response_fields[additional_status_code] = response_field
diff --git a/fastapi/utils.py b/fastapi/utils.py
index 8eacb83d1..530b5eca6 100644
--- a/fastapi/utils.py
+++ b/fastapi/utils.py
@@ -3,17 +3,12 @@ from typing import Any, Dict, List, Sequence, Set, Type
 
 from fastapi import routing
 from fastapi.openapi.constants import REF_PREFIX
-from pydantic import BaseConfig, BaseModel
+from pydantic import BaseModel
 from pydantic.fields import Field
 from pydantic.schema import get_flat_models_from_fields, model_process_schema
 from starlette.routing import BaseRoute
 
 
-class UnconstrainedConfig(BaseConfig):
-    min_anystr_length = None
-    max_anystr_length = None
-
-
 def get_flat_models_from_routes(
     routes: Sequence[Type[BaseRoute]]
 ) -> Set[Type[BaseModel]]: