From 7aebf023710c1744dfff4953177d9baabefd3174 Mon Sep 17 00:00:00 2001
From: Jamis Buck <jamis.buck@mongodb.com>
Date: Wed, 8 Nov 2023 13:19:00 -0700
Subject: [PATCH] Set support requires a bit of baby-sitting...

---
 lib/mongoid/fields/foreign_key.rb | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/mongoid/fields/foreign_key.rb b/lib/mongoid/fields/foreign_key.rb
index 2b8b558a90..815d5cdc99 100644
--- a/lib/mongoid/fields/foreign_key.rb
+++ b/lib/mongoid/fields/foreign_key.rb
@@ -134,6 +134,8 @@ def resizable?
       # @return [ Object ] The converted object.
       def mongoize_foreign_key(object)
         if type == Array || type == Set
+          object = object.to_a if type == Set || object.is_a?(Set)
+
           if object.resizable?
             object.blank? ? object : association.convert_to_foreign_key(object)
           else