diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5939cb0..ef2cef0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## 0.5
 
+### 0.5.3
+
+- Fix postgre alter null. (#142)
+
 ### 0.5.2
 
 - Fix rename field on the field add. (#134)
diff --git a/aerich/__init__.py b/aerich/__init__.py
index 7225152..43a1e95 100644
--- a/aerich/__init__.py
+++ b/aerich/__init__.py
@@ -1 +1 @@
-__version__ = "0.5.2"
+__version__ = "0.5.3"
diff --git a/aerich/ddl/__init__.py b/aerich/ddl/__init__.py
index 403bfc2..7e7740c 100644
--- a/aerich/ddl/__init__.py
+++ b/aerich/ddl/__init__.py
@@ -227,10 +227,10 @@ class BaseDDL:
         )
 
     def alter_column_null(self, model: "Type[Model]", field_describe: dict):
-        raise NotImplementedError
+        return self.modify_column(model, field_describe)
 
     def set_comment(self, model: "Type[Model]", field_describe: dict):
-        raise NotImplementedError
+        return self.modify_column(model, field_describe)
 
     def rename_table(self, model: "Type[Model]", old_table_name: str, new_table_name: str):
         db_table = model._meta.db_table
diff --git a/aerich/ddl/mysql/__init__.py b/aerich/ddl/mysql/__init__.py
index 57e607a..0cce776 100644
--- a/aerich/ddl/mysql/__init__.py
+++ b/aerich/ddl/mysql/__init__.py
@@ -1,10 +1,6 @@
-from typing import Type
-
-from tortoise import Model
 from tortoise.backends.mysql.schema_generator import MySQLSchemaGenerator
 
 from aerich.ddl import BaseDDL
-from aerich.exceptions import NotSupportError
 
 
 class MysqlDDL(BaseDDL):
@@ -29,9 +25,3 @@ class MysqlDDL(BaseDDL):
     _M2M_TABLE_TEMPLATE = "CREATE TABLE `{table_name}` (`{backward_key}` {backward_type} NOT NULL REFERENCES `{backward_table}` (`{backward_field}`) ON DELETE CASCADE,`{forward_key}` {forward_type} NOT NULL REFERENCES `{forward_table}` (`{forward_field}`) ON DELETE CASCADE){extra}{comment}"
     _MODIFY_COLUMN_TEMPLATE = "ALTER TABLE `{table_name}` MODIFY COLUMN {column}"
     _RENAME_TABLE_TEMPLATE = "ALTER TABLE `{old_table_name}` RENAME TO `{new_table_name}`"
-
-    def alter_column_null(self, model: "Type[Model]", field_describe: dict):
-        raise NotSupportError("Alter column null is unsupported in MySQL.")
-
-    def set_comment(self, model: "Type[Model]", field_describe: dict):
-        raise NotSupportError("Alter column comment is unsupported in MySQL.")
diff --git a/aerich/migrate.py b/aerich/migrate.py
index eb06b5e..e8ec20d 100644
--- a/aerich/migrate.py
+++ b/aerich/migrate.py
@@ -399,6 +399,9 @@ class Migrate:
                         elif option == "unique":
                             # because indexed include it
                             pass
+                        elif option == "nullable":
+                            # change nullable
+                            cls._add_operator(cls._alter_null(model, new_data_field), upgrade)
                         else:
                             # modify column
                             cls._add_operator(
diff --git a/pyproject.toml b/pyproject.toml
index 4916628..523c12d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "aerich"
-version = "0.5.2"
+version = "0.5.3"
 description = "A database migrations tool for Tortoise ORM."
 authors = ["long2ice <long2ice@gmail.com>"]
 license = "Apache-2.0"
diff --git a/tests/test_migrate.py b/tests/test_migrate.py
index 20ac113..71ac5bc 100644
--- a/tests/test_migrate.py
+++ b/tests/test_migrate.py
@@ -832,7 +832,7 @@ def test_migrate(mocker: MockerFixture):
     elif isinstance(Migrate.ddl, PostgresDDL):
         assert sorted(Migrate.upgrade_operators) == sorted(
             [
-                'ALTER TABLE "category" ALTER COLUMN "name" TYPE VARCHAR(200) USING "name"::VARCHAR(200)',
+                'ALTER TABLE "category" ALTER COLUMN "name" DROP NOT NULL',
                 'ALTER TABLE "category" ALTER COLUMN "slug" TYPE VARCHAR(100) USING "slug"::VARCHAR(100)',
                 'ALTER TABLE "config" ADD "user_id" INT NOT NULL',
                 'ALTER TABLE "config" ADD CONSTRAINT "fk_config_user_17daa970" FOREIGN KEY ("user_id") REFERENCES "user" ("id") ON DELETE CASCADE',
@@ -855,7 +855,7 @@ def test_migrate(mocker: MockerFixture):
         )
         assert sorted(Migrate.downgrade_operators) == sorted(
             [
-                'ALTER TABLE "category" ALTER COLUMN "name" TYPE VARCHAR(200) USING "name"::VARCHAR(200)',
+                'ALTER TABLE "category" ALTER COLUMN "name" SET NOT NULL',
                 'ALTER TABLE "category" ALTER COLUMN "slug" TYPE VARCHAR(200) USING "slug"::VARCHAR(200)',
                 'ALTER TABLE "user" ALTER COLUMN "password" TYPE VARCHAR(200) USING "password"::VARCHAR(200)',
                 'ALTER TABLE "config" DROP COLUMN "user_id"',