diff --git a/CHANGELOG b/CHANGELOG
index 89385eac..cf065224 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -11,6 +11,7 @@ https://dev.louiz.org/projects/poezio/roadmap
 - Contacts won’t be seen playing games or music when they actually stop doing
   so.
 - /leave now toggles off the autojoin flag instead of removing the bookmark.
+- Only add auotjoin on new bookmarks for synchronise_open_rooms on /join
 - /affiliation displays things in the info win instead of directly in the room,
   and additionally displays which room it refers to.
 - List the correct required versions for package maintainers.
diff --git a/poezio/bookmarks.py b/poezio/bookmarks.py
index ccda2b93..d842d2dd 100644
--- a/poezio/bookmarks.py
+++ b/poezio/bookmarks.py
@@ -171,7 +171,7 @@ class BookmarkList:
             return self.bookmarks[key]
         return None
 
-    def __in__(self, key) -> bool:
+    def __contains__(self, key) -> bool:
         if isinstance(key, (str, JID)):
             for bookmark in self.bookmarks:
                 if bookmark.jid == key:
diff --git a/poezio/core/commands.py b/poezio/core/commands.py
index 176d0e73..6fc800ae 100644
--- a/poezio/core/commands.py
+++ b/poezio/core/commands.py
@@ -401,7 +401,7 @@ class CommandCore:
                 tab.password = password
                 tab.join()
 
-        if config.get('synchronise_open_rooms'):
+        if config.get('synchronise_open_rooms') and room not in self.core.bookmarks:
             method = 'remote' if config.get(
                 'use_remote_bookmarks') else 'local'
             self._add_bookmark('%s/%s' % (room, nick), True, password, method)