diff --git a/app/services/post_alerter.rb b/app/services/post_alerter.rb
index c062bb6b448..77ef4146025 100644
--- a/app/services/post_alerter.rb
+++ b/app/services/post_alerter.rb
@@ -178,12 +178,26 @@ class PostAlerter
                SELECT last_read_post_number FROM topic_users tu
                WHERE tu.user_id = ? AND tu.topic_id = ? ),0)',
                 user.id, topic.id)
-      .where('reply_to_user_id = ? OR exists(
-            SELECT 1 from topic_users tu
-            WHERE tu.user_id = ? AND
-              tu.topic_id = ? AND
-              notification_level = ?
-            )', user.id, user.id, topic.id, TopicUser.notification_levels[:watching])
+      .where('reply_to_user_id = :user_id
+        OR exists(SELECT 1 from topic_users tu
+                  WHERE tu.user_id = :user_id AND
+                    tu.topic_id = :topic_id AND
+                    notification_level = :topic_level)
+        OR exists(SELECT 1 from category_users cu
+                  WHERE cu.user_id = :user_id AND
+                    cu.category_id = :category_id AND
+                    notification_level = :category_level)
+        OR exists(SELECT 1 from tag_users tu
+                  WHERE tu.user_id = :user_id AND
+                    tu.tag_id IN (SELECT tag_id FROM topic_tags WHERE topic_id = :topic_id) AND
+                    notification_level = :tag_level)',
+        user_id: user.id,
+        topic_id: topic.id,
+        category_id: topic.category_id,
+        topic_level: TopicUser.notification_levels[:watching],
+        category_level: CategoryUser.notification_levels[:watching],
+        tag_level: TagUser.notification_levels[:watching]
+      )
       .where(topic_id: topic.id)
   end
 
diff --git a/spec/services/post_alerter_spec.rb b/spec/services/post_alerter_spec.rb
index 8d492c14b73..86ca47e0187 100644
--- a/spec/services/post_alerter_spec.rb
+++ b/spec/services/post_alerter_spec.rb
@@ -1101,6 +1101,26 @@ describe PostAlerter do
         }.to add_notification(staged_member, :posted)
           .and not_add_notification(staged_non_member, :posted)
       end
+
+      it "does not update existing unread notification" do
+        category = Fabricate(:category)
+        CategoryUser.set_notification_level_for_category(user, CategoryUser.notification_levels[:watching], category.id)
+        topic = Fabricate(:topic, category: category)
+
+        post = Fabricate(:post, topic: topic)
+        PostAlerter.post_created(post)
+        notification = Notification.last
+        expect(notification.topic_id).to eq(topic.id)
+        expect(notification.post_number).to eq(1)
+
+        post = Fabricate(:post, topic: topic)
+        PostAlerter.post_created(post)
+        notification = Notification.last
+        expect(notification.topic_id).to eq(topic.id)
+        expect(notification.post_number).to eq(1)
+        notification_data = JSON.parse(notification.data)
+        expect(notification_data["display_username"]).to eq(I18n.t("embed.replies", count: 2))
+      end
     end
   end
 
@@ -1118,6 +1138,26 @@ describe PostAlerter do
         end
         expect(events).to include(event_name: :before_create_notifications_for_users, params: [[user], post])
       end
+
+      it "does not update existing unread notification" do
+        tag = Fabricate(:tag)
+        TagUser.change(user.id, tag.id, TagUser.notification_levels[:watching])
+        topic = Fabricate(:topic, tags: [tag])
+
+        post = Fabricate(:post, topic: topic)
+        PostAlerter.post_created(post)
+        notification = Notification.last
+        expect(notification.topic_id).to eq(topic.id)
+        expect(notification.post_number).to eq(1)
+
+        post = Fabricate(:post, topic: topic)
+        PostAlerter.post_created(post)
+        notification = Notification.last
+        expect(notification.topic_id).to eq(topic.id)
+        expect(notification.post_number).to eq(1)
+        notification_data = JSON.parse(notification.data)
+        expect(notification_data["display_username"]).to eq(I18n.t("embed.replies", count: 2))
+      end
     end
 
     context "on change" do