diff --git a/config/locales/server.en.yml b/config/locales/server.en.yml
index 4dae96ad89d..9e61260cc64 100644
--- a/config/locales/server.en.yml
+++ b/config/locales/server.en.yml
@@ -151,6 +151,7 @@ en:
     other: "Sorry, new users can only put %{count} links in a post."
   spamming_host: "Sorry you cannot post a link to that host."
   user_is_suspended: "Suspended users are not allowed to post."
+  topic_not_found: "Something has gone wrong. Perhaps this topic was closed or deleted while you were looking at it?"
 
   just_posted_that: "is too similar to what you recently posted"
   has_already_been_used: "has already been used"
@@ -2322,4 +2323,3 @@ en:
         Flagging is critical to the health of your community. If you notice any posts that require moderator attention please
         do not hesitate to flag. You may also use the flagging dialog to send <b>private messages</b> to users once you reach
         trust level 1.
-
diff --git a/lib/post_creator.rb b/lib/post_creator.rb
index 4bc5e7d8f0e..fb001810c7a 100644
--- a/lib/post_creator.rb
+++ b/lib/post_creator.rb
@@ -205,7 +205,11 @@ class PostCreator
       end
     else
       topic = Topic.find_by(id: @opts[:topic_id])
-      guardian.ensure_can_create!(Post, topic)
+      if (topic.blank? || !guardian.can_create?(Post, topic))
+        @errors = Post.new.errors
+        @errors.add(:base, I18n.t(:topic_not_found))
+        raise ActiveRecord::Rollback.new
+      end
     end
     @topic = topic
   end
diff --git a/spec/components/post_creator_spec.rb b/spec/components/post_creator_spec.rb
index ef5d4f0c545..77d658f08c5 100644
--- a/spec/components/post_creator_spec.rb
+++ b/spec/components/post_creator_spec.rb
@@ -332,7 +332,10 @@ describe PostCreator do
 
     it 'ensures the user can create the post' do
       Guardian.any_instance.expects(:can_create?).with(Post, topic).returns(false)
-      expect { creator.create }.to raise_error(Discourse::InvalidAccess)
+      post = creator.create
+      expect(post).to be_blank
+      expect(creator.errors.count).to eq 1
+      expect(creator.errors.messages[:base][0]).to match I18n.t(:topic_not_found)
     end
 
     context 'success' do
@@ -347,6 +350,30 @@ describe PostCreator do
 
   end
 
+  context 'closed topic' do
+    let!(:topic) { Fabricate(:topic, user: user, closed: true) }
+    let(:creator) { PostCreator.new(user, raw: 'test reply', topic_id: topic.id, reply_to_post_number: 4) }
+
+    it 'responds with an error message' do
+      post = creator.create
+      expect(post).to be_blank
+      expect(creator.errors.count).to eq 1
+      expect(creator.errors.messages[:base][0]).to match I18n.t(:topic_not_found)
+    end
+  end
+
+  context 'missing topic' do
+    let!(:topic) { Fabricate(:topic, user: user, deleted_at: 5.minutes.ago) }
+    let(:creator) { PostCreator.new(user, raw: 'test reply', topic_id: topic.id, reply_to_post_number: 4) }
+
+    it 'responds with an error message' do
+      post = creator.create
+      expect(post).to be_blank
+      expect(creator.errors.count).to eq 1
+      expect(creator.errors.messages[:base][0]).to match I18n.t(:topic_not_found)
+    end
+  end
+
   context "cooking options" do
     let(:raw) { "this is my awesome message body hello world" }
 
diff --git a/spec/integration/spam_rules_spec.rb b/spec/integration/spam_rules_spec.rb
index 022b0fd7439..58d995141dd 100644
--- a/spec/integration/spam_rules_spec.rb
+++ b/spec/integration/spam_rules_spec.rb
@@ -41,7 +41,7 @@ describe SpamRulesEnforcer do
 
           Invariant { expect(Guardian.new(spammer).can_create_topic?(nil)).to be false }
           Invariant { expect{PostCreator.create(spammer, {title: 'limited time offer for you', raw: 'better buy this stuff ok', archetype_id: 1})}.to raise_error(Discourse::InvalidAccess) }
-          Invariant { expect{PostCreator.create(spammer, {topic_id: another_topic.id, raw: 'my reply is spam in your topic', archetype_id: 1})}.to raise_error(Discourse::InvalidAccess) }
+          Invariant { PostCreator.create(spammer, {topic_id: another_topic.id, raw: 'my reply is spam in your topic', archetype_id: 1}).should == nil }
 
           Then { expect(spammer.reload).to be_blocked }
           And  { expect(spam_post.reload).to be_hidden }