diff --git a/lib/submissions/generate_result_attachments.rb b/lib/submissions/generate_result_attachments.rb
index ee7405e8..bc2ea682 100644
--- a/lib/submissions/generate_result_attachments.rb
+++ b/lib/submissions/generate_result_attachments.rb
@@ -344,7 +344,7 @@ module Submissions
 
       if tsa_url
         params[:timestamp_handler] = Submissions::TimestampHandler.new(tsa_url:)
-        params[:signature_size] = 10_000
+        params[:signature_size] = 20_000
       end
 
       params