diff --git a/README.md b/README.md
index f2c1e27..94074dc 100644
--- a/README.md
+++ b/README.md
@@ -231,6 +231,7 @@ You can use `aerich` out of cli by use `Command` class.
 from aerich import Command
 
 command = Command(tortoise_config=config, app='models')
+await command.init()
 await command.migrate('test')
 ```
 
diff --git a/aerich/__init__.py b/aerich/__init__.py
index 0b874be..ba30abf 100644
--- a/aerich/__init__.py
+++ b/aerich/__init__.py
@@ -27,7 +27,7 @@ class Command:
     def __init__(
         self,
         tortoise_config: dict,
-        app: str,
+        app: str = "models",
         location: str = "./migrations",
         src_folder: str = ".",
     ):