diff --git a/maubot/instance.py b/maubot/instance.py
index 6e3590f..11c53bd 100644
--- a/maubot/instance.py
+++ b/maubot/instance.py
@@ -170,6 +170,8 @@ class PluginInstance:
             self.plugin.on_external_config_update()
 
     async def update_primary_user(self, primary_user: UserID) -> bool:
+        if not primary_user or primary_user == self.primary_user:
+            return True
         client = Client.get(primary_user)
         if not client:
             return False
diff --git a/maubot/management/api/instance.py b/maubot/management/api/instance.py
index 2947247..2901b8c 100644
--- a/maubot/management/api/instance.py
+++ b/maubot/management/api/instance.py
@@ -65,7 +65,7 @@ async def _create_instance(instance_id: str, data: dict) -> web.Response:
 
 
 async def _update_instance(instance: PluginInstance, data: dict) -> web.Response:
-    if not await instance.update_primary_user(data.get("primary_user")):
+    if not await instance.update_primary_user(data.get("primary_user", None)):
         return ErrPrimaryUserNotFound
     instance.update_id(data.get("id", None))
     instance.update_enabled(data.get("enabled", None))