diff --git a/lib/topics_bulk_action.rb b/lib/topics_bulk_action.rb
index a26dc0eb0a..5c45a01c9b 100644
--- a/lib/topics_bulk_action.rb
+++ b/lib/topics_bulk_action.rb
@@ -68,9 +68,10 @@ class TopicsBulkAction
   end
 
   def dismiss_posts
+    highest_number_source_column = @user.staff? ? 'highest_staff_post_number' : 'highest_post_number'
     sql = <<~SQL
       UPDATE topic_users tu
-      SET highest_seen_post_number = t.highest_post_number , last_read_post_number = highest_post_number
+      SET highest_seen_post_number = t.#{highest_number_source_column} , last_read_post_number = t.#{highest_number_source_column}
       FROM topics t
       WHERE t.id = tu.topic_id AND tu.user_id = :user_id AND t.id IN (:topic_ids)
     SQL
diff --git a/spec/components/topics_bulk_action_spec.rb b/spec/components/topics_bulk_action_spec.rb
index b0788c8b78..58cc96283c 100644
--- a/spec/components/topics_bulk_action_spec.rb
+++ b/spec/components/topics_bulk_action_spec.rb
@@ -20,6 +20,32 @@ describe TopicsBulkAction do
       expect(tu.last_read_post_number).to eq(3)
       expect(tu.highest_seen_post_number).to eq(3)
     end
+
+    context "when the user is staff" do
+      fab!(:user) { Fabricate(:admin) }
+
+      context "when the highest_staff_post_number is > highest_post_number for a topic (e.g. whisper is last post)" do
+        it "dismisses posts" do
+          post1 = create_post(user: user)
+          p = create_post(topic_id: post1.topic_id)
+          create_post(topic_id: post1.topic_id)
+
+          whisper = PostCreator.new(
+            user,
+            topic_id: post1.topic.id,
+            post_type: Post.types[:whisper],
+            raw: 'this is a whispered reply'
+          ).create
+
+          TopicsBulkAction.new(user, [post1.topic_id], type: 'dismiss_posts').perform!
+
+          tu = TopicUser.find_by(user_id: user.id, topic_id: post1.topic_id)
+
+          expect(tu.last_read_post_number).to eq(4)
+          expect(tu.highest_seen_post_number).to eq(4)
+        end
+      end
+    end
   end
 
   describe "invalid operation" do