diff --git a/ormar/fields/base.py b/ormar/fields/base.py
index 95645c0..155b1c9 100644
--- a/ormar/fields/base.py
+++ b/ormar/fields/base.py
@@ -93,9 +93,11 @@ class BaseField(FieldInfo):
         :rtype: bool
         """
         return (
-            field_name not in ["default", "default_factory", "alias"]
-            and not field_name.startswith("__")
-            and hasattr(cls, field_name)
+                field_name not in ["default", "default_factory", "alias",
+                                   "allow_mutation"]
+                and not field_name.startswith("__")
+                and hasattr(cls, field_name)
+                and not callable(getattr(cls, field_name))
         )
 
     @classmethod
@@ -204,7 +206,7 @@ class BaseField(FieldInfo):
         :rtype: bool
         """
         return cls.default is not None or (
-            cls.server_default is not None and use_server
+                cls.server_default is not None and use_server
         )
 
     @classmethod
@@ -237,7 +239,7 @@ class BaseField(FieldInfo):
                 ondelete=con.ondelete,
                 onupdate=con.onupdate,
                 name=f"fk_{cls.owner.Meta.tablename}_{cls.to.Meta.tablename}"
-                f"_{cls.to.get_column_alias(cls.to.Meta.pkname)}_{cls.name}",
+                     f"_{cls.to.get_column_alias(cls.to.Meta.pkname)}_{cls.name}",
             )
             for con in cls.constraints
         ]
@@ -270,10 +272,10 @@ class BaseField(FieldInfo):
 
     @classmethod
     def expand_relationship(
-        cls,
-        value: Any,
-        child: Union["Model", "NewBaseModel"],
-        to_register: bool = True,
+            cls,
+            value: Any,
+            child: Union["Model", "NewBaseModel"],
+            to_register: bool = True,
     ) -> Any:
         """
         Function overwritten for relations, in basic field the value is returned as is.
@@ -301,7 +303,7 @@ class BaseField(FieldInfo):
         :rtype: None
         """
         if cls.owner is not None and (
-            cls.owner == cls.to or cls.owner.Meta == cls.to.Meta
+                cls.owner == cls.to or cls.owner.Meta == cls.to.Meta
         ):
             cls.self_reference = True
             cls.self_reference_primary = cls.name
diff --git a/setup.py b/setup.py
index 909a738..2c5c25b 100644
--- a/setup.py
+++ b/setup.py
@@ -52,8 +52,11 @@ setup(
     package_data={PACKAGE: ["py.typed"]},
     include_package_data=True,
     zip_safe=False,
+    python_requires=">=3.6",
     data_files=[("", ["LICENSE.md"])],
-    install_requires=["databases", "pydantic>=1.5", "sqlalchemy", "typing_extensions"],
+    install_requires=["databases>=0.3.2,<=0.4.1", "pydantic>=1.6.1,<=1.8",
+                      "sqlalchemy>=1.3.18,<=1.3.23",
+                      "typing_extensions>=3.7,<=3.7.4.3"],
     extras_require={
         "postgresql": ["asyncpg", "psycopg2"],
         "mysql": ["aiomysql", "pymysql"],