diff --git a/.coverage b/.coverage
index d8930bb..b5b4f93 100644
Binary files a/.coverage and b/.coverage differ
diff --git a/orm/fields/base.py b/orm/fields/base.py
index 9d321f2..d405679 100644
--- a/orm/fields/base.py
+++ b/orm/fields/base.py
@@ -1,4 +1,4 @@
-from typing import Any, Dict, List, Optional, TYPE_CHECKING, Type
+from typing import Any, Dict, List, Optional, TYPE_CHECKING
 
 import sqlalchemy
 
@@ -8,27 +8,6 @@ if TYPE_CHECKING:  # pragma no cover
     from orm.models import Model
 
 
-class RequiredParams:
-    def __init__(self, *args: str) -> None:
-        self._required = list(args)
-
-    def __call__(self, model_field_class: Type["BaseField"]) -> Type["BaseField"]:
-        old_init = model_field_class.__init__
-        model_field_class._old_init = old_init
-
-        def __init__(instance: "BaseField", *args: Any, **kwargs: Any) -> None:
-            super(instance.__class__, instance).__init__(*args, **kwargs)
-            for arg in self._required:
-                if arg not in kwargs:
-                    raise ModelDefinitionError(
-                        f"{instance.__class__.__name__} field requires parameter: {arg}"
-                    )
-                setattr(instance, arg, kwargs.pop(arg))
-
-        model_field_class.__init__ = __init__
-        return model_field_class
-
-
 class BaseField:
     __type__ = None
 
diff --git a/orm/fields/foreign_key.py b/orm/fields/foreign_key.py
index 0788ce2..b32a887 100644
--- a/orm/fields/foreign_key.py
+++ b/orm/fields/foreign_key.py
@@ -11,7 +11,7 @@ if TYPE_CHECKING:  # pragma no cover
     from orm.models import Model
 
 
-def create_dummy_instance(fk: Type["Model"], pk: int = None) -> "Model":
+def create_dummy_instance(fk: Type["Model"], pk: Any = None) -> "Model":
     init_dict = {
         **{fk.__pkname__: pk or -1},
         **{
diff --git a/orm/fields/model_fields.py b/orm/fields/model_fields.py
index 813f190..4d841e1 100644
--- a/orm/fields/model_fields.py
+++ b/orm/fields/model_fields.py
@@ -4,7 +4,8 @@ import decimal
 import sqlalchemy
 from pydantic import Json
 
-from orm.fields.base import BaseField, RequiredParams  # noqa I101
+from orm.fields.base import BaseField  # noqa I101
+from orm.fields.required_decorator import RequiredParams
 
 
 @RequiredParams("length")
diff --git a/orm/fields/required_decorator.py b/orm/fields/required_decorator.py
new file mode 100644
index 0000000..4deb597
--- /dev/null
+++ b/orm/fields/required_decorator.py
@@ -0,0 +1,27 @@
+from typing import Any, TYPE_CHECKING, Type
+
+from orm import ModelDefinitionError
+
+if TYPE_CHECKING:  # pragma no cover
+    from orm.fields import BaseField
+
+
+class RequiredParams:
+    def __init__(self, *args: str) -> None:
+        self._required = list(args)
+
+    def __call__(self, model_field_class: Type["BaseField"]) -> Type["BaseField"]:
+        old_init = model_field_class.__init__
+        model_field_class._old_init = old_init
+
+        def __init__(instance: "BaseField", *args: Any, **kwargs: Any) -> None:
+            super(instance.__class__, instance).__init__(*args, **kwargs)
+            for arg in self._required:
+                if arg not in kwargs:
+                    raise ModelDefinitionError(
+                        f"{instance.__class__.__name__} field requires parameter: {arg}"
+                    )
+                setattr(instance, arg, kwargs.pop(arg))
+
+        model_field_class.__init__ = __init__
+        return model_field_class