diff --git a/app/models/post_action.rb b/app/models/post_action.rb
index 766d072ab..ac3f68779 100644
--- a/app/models/post_action.rb
+++ b/app/models/post_action.rb
@@ -124,6 +124,11 @@ class PostAction < ActiveRecord::Base
     end
   end
 
+  def remove_act!(user)
+    trash!
+    run_callbacks(:save)
+  end
+
   def is_bookmark?
     post_action_type_id == PostActionType.types[:bookmark]
   end
diff --git a/lib/post_creator.rb b/lib/post_creator.rb
index e1835ce0f..c48073f59 100644
--- a/lib/post_creator.rb
+++ b/lib/post_creator.rb
@@ -105,6 +105,8 @@ class PostCreator
         topic.allowed_users.where(["users.email_private_messages = true and users.id != ?", @user.id]).each do |u|
           Jobs.enqueue_in(SiteSetting.email_time_window_mins.minutes, :user_email, type: :private_message, user_id: u.id, post_id: post.id)
         end
+
+        clear_possible_flags(topic) if post.post_number > 1 && topic.user_id != post.user_id
       end
 
       # Track the topic
@@ -148,6 +150,25 @@ class PostCreator
 
   protected
 
+  def clear_possible_flags(topic)
+    # at this point we know the topic is a PM and has been replied to ... check if we need to clear any flags
+    #
+    first_post = Post.select(:id).where(topic_id: topic.id).where('post_number = 1').first
+    post_action = nil
+
+    if first_post
+      post_action = PostAction.where(
+        related_post_id: first_post.id,
+        deleted_at: nil,
+        post_action_type_id: PostActionType.types[:notify_moderators]
+      ).first
+    end
+
+    if post_action
+      post_action.remove_act!(@user)
+    end
+  end
+
   def add_users(topic, usernames)
     return unless usernames
     usernames = usernames.split(',')
diff --git a/spec/models/post_action_spec.rb b/spec/models/post_action_spec.rb
index 3e74c3698..8183efc4c 100644
--- a/spec/models/post_action_spec.rb
+++ b/spec/models/post_action_spec.rb
@@ -24,7 +24,7 @@ describe PostAction do
       action = PostAction.act(codinghorror, post, PostActionType.types[:notify_moderators], "this is my special long message");
 
       posts = Post.joins(:topic)
-                  .select('posts.id, topics.subtype')
+                  .select('posts.id, topics.subtype, posts.topic_id')
                   .where('topics.archetype' => Archetype.private_message)
                   .to_a
 
@@ -32,6 +32,13 @@ describe PostAction do
       action.related_post_id.should == posts[0].id.to_i
       posts[0].subtype.should == TopicSubtype.notify_moderators
 
+      # reply to PM should clear flag
+      p = PostCreator.new(mod, topic_id: posts[0].topic_id, raw: "This is my test reply to the user, it should clear flags")
+      p.create
+
+      action.reload
+      action.deleted_at.should_not be_nil
+
     end
 
     describe 'notify_moderators' do