diff --git a/app/models/discussion_topic.rb b/app/models/discussion_topic.rb
index a47680dc974..c74fc244648 100644
--- a/app/models/discussion_topic.rb
+++ b/app/models/discussion_topic.rb
@@ -37,7 +37,7 @@ class DiscussionTopic < ActiveRecord::Base
   include LockedFor
 
   restrict_columns :content, [:title, :message]
-  restrict_columns :settings, [:delayed_post_at, :require_initial_post, :discussion_type,
+  restrict_columns :settings, [:delayed_post_at, :require_initial_post, :discussion_type, :assignment_id,
                                :lock_at, :pinned, :locked, :allow_rating, :only_graders_can_rate, :sort_by_rating]
   restrict_columns :state, [:workflow_state]
   restrict_assignment_columns
@@ -272,7 +272,15 @@ class DiscussionTopic < ActiveRecord::Base
     end
     if @old_assignment_id
       Assignment.where(:id => @old_assignment_id, :context_id => self.context_id, :context_type => self.context_type, :submission_types => 'discussion_topic').update_all(:workflow_state => 'deleted', :updated_at => Time.now.utc)
-      ContentTag.delete_for(Assignment.find(@old_assignment_id)) if @old_assignment_id
+      old_assignment = Assignment.find(@old_assignment_id)
+      ContentTag.delete_for(old_assignment)
+      # prevent future syncs from recreating the deleted assignment
+      if is_child_content?
+        old_assignment.submission_types = 'none'
+        context.master_course_subscriptions.each do |sub|
+          sub.create_content_tag_for!(old_assignment, :downstream_changes => ['workflow_state'])
+        end
+      end
     elsif self.assignment && @saved_by != :assignment && !self.root_topic_id
       deleted_assignment = self.assignment.deleted?
       self.sync_assignment
diff --git a/spec/models/master_courses/master_migration_spec.rb b/spec/models/master_courses/master_migration_spec.rb
index 84cd88182ae..d3cd7909132 100644
--- a/spec/models/master_courses/master_migration_spec.rb
+++ b/spec/models/master_courses/master_migration_spec.rb
@@ -1133,6 +1133,36 @@ describe MasterCourses::MasterMigration do
       expect(copied_topic_assmt.reload.due_at.to_i).to eq new_master_due_at.to_i
     end
 
+    it "allows a minion course's change of the graded status of a discussion topic to stick" do
+      @copy_to = course_factory
+      sub = @template.add_child_course!(@copy_to)
+
+      topic = @copy_from.discussion_topics.new
+      topic.assignment = @copy_from.assignments.build(:due_at => 1.month.from_now)
+      topic.save!
+      run_master_migration
+
+      topic_to = @copy_to.discussion_topics.where(:migration_id => mig_id(topic)).take
+      assignment_to = topic_to.assignment
+      topic_to.assignment = nil
+      topic_to.save!
+
+      expect(assignment_to.reload).to be_deleted
+      topic_tag = MasterCourses::ChildContentTag.where(content_type: 'DiscussionTopic', content_id: topic_to.id).take
+      expect(topic_tag.downstream_changes).to include 'assignment_id'
+      assign_tag = MasterCourses::ChildContentTag.where(content_id: 'Assignment', content_id: assignment_to.id).take
+      expect(assign_tag.downstream_changes).to include 'workflow_state'
+
+      Timecop.travel(1.hour.from_now) do
+        topic.message = 'content updated'
+        topic.save!
+      end
+      run_master_migration
+
+      expect(topic_to.reload.assignment).to be_nil
+      expect(assignment_to.reload).to be_deleted
+    end
+
     it "should ignore course settings on selective export unless requested" do
       @copy_to = course_factory
       @sub = @template.add_child_course!(@copy_to)