diff --git a/matrix_appservice_kakaotalk/commands/auth.py b/matrix_appservice_kakaotalk/commands/auth.py
index e746f7d..6b76e62 100644
--- a/matrix_appservice_kakaotalk/commands/auth.py
+++ b/matrix_appservice_kakaotalk/commands/auth.py
@@ -69,8 +69,13 @@ async def login(evt: CommandEvent) -> None:
         await evt.reply("You're already logged in")
         return
 
-    save = len(evt.args) > 0 and evt.args[0] == "--save"
-    email = evt.args[0 if not save else 1] if len(evt.args) > 0 else None
+    num_args = len(evt.args)
+    save = num_args > 0 and evt.args[0] == "--save"
+    # TODO Once web login is implemented, don't make <email> a mandatory argument
+    if not save and num_args != 1:
+        await evt.reply("**Usage:** `$cmdprefix+sp login [--save] <email>`")
+        return
+    email = evt.args[0 if not save else 1] if num_args > 0 else None
 
     if email:
         evt.sender.command_status = {