diff --git a/script/bulk_import/discourse_merger.rb b/script/bulk_import/discourse_merger.rb
index 0cf9713950c..ae40b36a8ac 100644
--- a/script/bulk_import/discourse_merger.rb
+++ b/script/bulk_import/discourse_merger.rb
@@ -601,13 +601,11 @@ class BulkImport::DiscourseMerger < BulkImport::Base
   def process_post_upload(post_upload)
     return nil unless post_upload['upload_id'].present?
 
-    # can't figure out why there are duplicates of these during merge.
-    # here's a hack to prevent it:
     @imported_post_uploads ||= {}
-    return nil if @imported_post_uploads[post_upload['post_id']] == post_upload['upload_id']
-    @imported_post_uploads[post_upload['post_id']] = post_upload['upload_id']
+    return nil if @imported_post_uploads[post_upload['post_id']]&.include?(post_upload['upload_id'])
+    @imported_post_uploads[post_upload['post_id']] ||= []
+    @imported_post_uploads[post_upload['post_id']] << post_upload['upload_id']
 
-    # ...and there are still duplicates. So try this:
     return nil if PostUpload.where(post_id: post_upload['post_id'], upload_id: post_upload['upload_id']).exists?
 
     post_upload