diff --git a/README.md b/README.md
index 2febe9f..3e227c1 100644
--- a/README.md
+++ b/README.md
@@ -95,6 +95,13 @@ The message that is sent when the webhook is triggered.
 Supports formatting [as defined below](#formatting).
 
 
+### `message_format`
+The format the message is interpreted as. Must be one of:
+- `plaintext` (default)
+- `markdown`
+- `html`
+
+
 ### `auth_type`
 This can be used to protect a webhook against unauthorized access.
 Can be one of `Basic` for HTTP basic auth with username and password or `Bearer` for bearer token auth.
@@ -108,13 +115,6 @@ If `auth_type` is `Basic`, this must be the username and password, separated by
 If `auth_type` is `Bearer`, this is the token used for token bearer authorization, so requests must carry an `Authorization: Bearer <token>` header.
 
 
-### `message_format`
-The format the message is interpreted as. Must be one of:
-- `plaintext` (default)
-- `markdown`
-- `html`
-
-
 ### `force_json`
 This setting takes a boolean and specifies whether the request body should be interpreted and parsed as json, even if the content type says otherwise.
 
diff --git a/base-config.yaml b/base-config.yaml
index 8b6da4d..387ce72 100644
--- a/base-config.yaml
+++ b/base-config.yaml
@@ -2,8 +2,8 @@ path: "/send"
 method: "POST"
 room: "!AAAAAAAAAAAAAAAAAA:example.com"
 message: "Hello world!"
+message_format: "plaintext"
 auth_type:
 auth_token:
-message_format: "plaintext"
 force_json: false
 ignore_empty_messages: false
diff --git a/plugin.py b/plugin.py
index cb6a765..12d7e1b 100644
--- a/plugin.py
+++ b/plugin.py
@@ -47,15 +47,22 @@ def do_update(self, helper: ConfigUpdateHelper) -> None:
         helper.copy("method")
         helper.copy("room")
         helper.copy("message")
+        helper.copy("message_format")
         helper.copy("auth_type")
         helper.copy("auth_token")
-        helper.copy("message_format")
         helper.copy("force_json")
         helper.copy("ignore_empty_messages")
 
         # validate base config as it also contains default values
         # for options not present in the source config.
 
+        # validate message_format
+        valid_message_formats = {"markdown", "plaintext", "html"}
+        message_format = helper.base["message_format"]
+        if message_format not in valid_message_formats:
+            raise ValueError(f"Invalid message_format '{message_format}' specified! "
+                             f"Must be one of: {', '.join(valid_message_formats)}")
+
         # validate auth_type and auth_token
         valid_auth_types = {"Basic", "Bearer"}
         auth_type = helper.base["auth_type"]
@@ -71,13 +78,6 @@ def do_update(self, helper: ConfigUpdateHelper) -> None:
                 raise ValueError(f"Invalid auth_token '{auth_token}' specified! For HTTP basic auth, it must contain "
                                  "a username and a password, separated by a colon (<username>:<password>).")
 
-        # validate message_format
-        valid_message_formats = {"markdown", "plaintext", "html"}
-        message_format = helper.base["message_format"]
-        if message_format not in valid_message_formats:
-            raise ValueError(f"Invalid message_format '{message_format}' specified! "
-                             f"Must be one of: {', '.join(valid_message_formats)}")
-
 
 class WebhookPlugin(Plugin):