diff --git a/app/assets/javascripts/discourse/app/controllers/topic.js b/app/assets/javascripts/discourse/app/controllers/topic.js
index 435da4d4032..dd5ed6e1428 100644
--- a/app/assets/javascripts/discourse/app/controllers/topic.js
+++ b/app/assets/javascripts/discourse/app/controllers/topic.js
@@ -1842,6 +1842,10 @@ export default class TopicController extends Controller.extend(
         }
         break;
       }
+      case "remove_allowed_user": {
+        this.router.transitionTo("userPrivateMessages", this.currentUser);
+        break;
+      }
       default: {
         let callback = customPostMessageCallbacks[data.type];
         if (callback) {
diff --git a/app/models/topic.rb b/app/models/topic.rb
index 3c602f2f0f8..dd35179ac07 100644
--- a/app/models/topic.rb
+++ b/app/models/topic.rb
@@ -1174,6 +1174,7 @@ class Topic < ActiveRecord::Base
         end
 
         topic_user.destroy
+        MessageBus.publish("/topic/#{id}", { type: "remove_allowed_user" }, user_ids: [user.id])
         return true
       end
     end
diff --git a/lib/guardian/post_guardian.rb b/lib/guardian/post_guardian.rb
index 89dade652ff..dad2ed9c986 100644
--- a/lib/guardian/post_guardian.rb
+++ b/lib/guardian/post_guardian.rb
@@ -164,6 +164,7 @@ module PostGuardian
     if (is_staff? || is_in_edit_post_groups? || is_category_group_moderator?(post.topic&.category))
       return can_create_post?(post.topic)
     end
+    return false if !can_see_post_topic?(post)
 
     return false if post.topic&.archived? || post.user_deleted || post.deleted_at
 
diff --git a/spec/lib/guardian/post_guardian_spec.rb b/spec/lib/guardian/post_guardian_spec.rb
index 9617c0355ef..b21def926d6 100644
--- a/spec/lib/guardian/post_guardian_spec.rb
+++ b/spec/lib/guardian/post_guardian_spec.rb
@@ -97,5 +97,14 @@ RSpec.describe PostGuardian do
       post.update!(user: anon)
       expect(Guardian.new(anon).can_edit_post?(post)).to eq(true)
     end
+
+    it "returns false if the user is the author, but can no longer see the post" do
+      post.update!(user: user)
+      guardian = Guardian.new(user)
+
+      guardian.stubs(:can_see_post_topic?).returns(false)
+
+      expect(guardian.can_edit_post?(post)).to eq(false)
+    end
   end
 end
diff --git a/spec/requests/posts_controller_spec.rb b/spec/requests/posts_controller_spec.rb
index 0791cfe1714..972454bd0c4 100644
--- a/spec/requests/posts_controller_spec.rb
+++ b/spec/requests/posts_controller_spec.rb
@@ -566,6 +566,13 @@ RSpec.describe PostsController do
         expect(response).to be_forbidden
       end
 
+      it "raises an error when user is OP but can no longer see the post" do
+        post = Fabricate(:private_message_post, user: user)
+        post.topic.remove_allowed_user(admin, user)
+        put "/posts/#{post.id}.json", params: update_params
+        expect(response).to be_forbidden
+      end
+
       it "updates post's raw attribute" do
         put "/posts/#{post.id}.json", params: { post: { raw: "edited body   " } }
 
diff --git a/spec/system/private_message_spec.rb b/spec/system/private_message_spec.rb
new file mode 100644
index 00000000000..40195690f9d
--- /dev/null
+++ b/spec/system/private_message_spec.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+describe "Private Message", type: :system do
+  let(:sender) { Fabricate(:user) }
+  let(:recipient) { Fabricate(:user) }
+
+  let(:post) { Fabricate(:private_message_post, user: sender, recipient: recipient) }
+
+  before { sign_in(recipient) }
+
+  context "when being removed from private conversation" do
+    it "redirects away from the private message" do
+      visit(post.full_url)
+
+      expect(page).to have_css("h1", text: post.topic.title)
+
+      post.topic.remove_allowed_user(sender, recipient)
+
+      expect(page).to have_no_css("h1", text: post.topic.title)
+      expect(page).to have_current_path("/u/#{recipient.username}/messages")
+    end
+  end
+end