From b8609a6d03aabcde75fb1874e1a6548d35cefbb7 Mon Sep 17 00:00:00 2001
From: Alejandro Casanovas <janscas@users.noreply.github.com>
Date: Mon, 22 Apr 2019 14:10:06 +0200
Subject: [PATCH] Fixed bug introduced in #231

---
 O365/message.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/O365/message.py b/O365/message.py
index c78229a77745..46a751601efe 100644
--- a/O365/message.py
+++ b/O365/message.py
@@ -542,7 +542,7 @@ def to_api_data(self, restrict_keys=None):
         if self.sender and self.sender.address:
             message[cc('from')] = self._recipient_to_cloud(self.sender)
 
-        if self.categories or 'categories' in restrict_keys:
+        if self.categories or 'categories' in (restrict_keys or {}):
             message[cc('categories')] = self.categories
 
         if self.object_id and not self.__is_draft: