diff --git a/orm/fields.py b/orm/fields.py
index 9015a76..6488f8b 100644
--- a/orm/fields.py
+++ b/orm/fields.py
@@ -16,13 +16,22 @@ def __init__(
         **kwargs: typing.Any,
     ) -> None:
         if primary_key:
-            kwargs["read_only"] = True
+            default_value = kwargs.get("default", None)
+            self.raise_if_pk_without_default(default_value)
+            kwargs['allow_null'] = True
+
         self.allow_null = kwargs.get("allow_null", False)
         self.primary_key = primary_key
         self.index = index
         self.unique = unique
         self.validator = self.get_validator(**kwargs)
 
+    def raise_if_pk_without_default(self, default: typing.Any):
+        if not default:
+            raise ValueError(
+                f"You need to specify default value for {self.__class__.__name__} primary key field"
+            )
+
     def get_column(self, name: str) -> sqlalchemy.Column:
         column_type = self.get_column_type()
         constraints = self.get_constraints()
@@ -70,6 +79,9 @@ def get_column_type(self):
 
 
 class Integer(ModelField):
+    def raise_if_pk_without_default(self, default: typing.Any):
+        pass
+
     def get_validator(self, **kwargs) -> typesystem.Field:
         return typesystem.Integer(**kwargs)
 
diff --git a/orm/models.py b/orm/models.py
index b402814..dd5c135 100644
--- a/orm/models.py
+++ b/orm/models.py
@@ -410,14 +410,14 @@ def _validate_kwargs(self, **kwargs):
         for key, value in fields.items():
             if value.validator.read_only and value.validator.has_default():
                 kwargs[key] = value.validator.get_default_value()
-        return kwargs
+
+        return {key: value for key, value in kwargs.items() if value is not None}
 
     async def create(self, **kwargs):
         kwargs = self._validate_kwargs(**kwargs)
         instance = self.model_cls(**kwargs)
         expr = self.table.insert().values(**kwargs)
-
-        if self.pkname not in kwargs:
+        if not self.pkname in kwargs:
             instance.pk = await self.database.execute(expr)
         else:
             await self.database.execute(expr)
diff --git a/tests/test_columns.py b/tests/test_columns.py
index 278aecd..54bb9b0 100644
--- a/tests/test_columns.py
+++ b/tests/test_columns.py
@@ -131,6 +131,12 @@ async def test_model_crud():
     assert product.updated_date == last_updated_date
 
 
+async def test_create_user_with_custom_uuid():
+    custom_uuid = uuid.uuid4()
+    user = await User.objects.create(id=custom_uuid)
+    assert user.pk == custom_uuid
+
+
 async def test_both_auto_now_and_auto_now_add_raise_error():
     with pytest.raises(ValueError):
 
@@ -159,3 +165,13 @@ async def test_bulk_create():
     assert products[1].data == {"foo": 456}
     assert products[1].value == 456.789
     assert products[1].status == StatusEnum.DRAFT
+
+
+async def test_create_with_pk_not_integer_and_without_default_value():
+    with pytest.raises(ValueError):
+
+        class Post(orm.Model):
+            registry = models
+            fields = {
+                "id": orm.UUID(primary_key=True)
+            }