diff --git a/app/controllers/reviewable_claimed_topics_controller.rb b/app/controllers/reviewable_claimed_topics_controller.rb
index eb8b0d712b5..37f66cd9b5e 100644
--- a/app/controllers/reviewable_claimed_topics_controller.rb
+++ b/app/controllers/reviewable_claimed_topics_controller.rb
@@ -6,7 +6,10 @@ class ReviewableClaimedTopicsController < ApplicationController
   def create
     topic = Topic.find_by(id: params[:reviewable_claimed_topic][:topic_id])
     guardian.ensure_can_claim_reviewable_topic!(topic)
-    ReviewableClaimedTopic.create!(user_id: current_user.id, topic_id: topic.id)
+    ReviewableClaimedTopic.create(user_id: current_user.id, topic_id: topic.id)
+    render json: success_json
+  rescue ActiveRecord::RecordNotUnique
+    # This is just in case the validation fails under concurrency
     render json: success_json
   end
 
diff --git a/app/models/reviewable_claimed_topic.rb b/app/models/reviewable_claimed_topic.rb
index 216aa6543c1..dc54c4abf14 100644
--- a/app/models/reviewable_claimed_topic.rb
+++ b/app/models/reviewable_claimed_topic.rb
@@ -3,6 +3,7 @@
 class ReviewableClaimedTopic < ActiveRecord::Base
   belongs_to :topic
   belongs_to :user
+  validates_uniqueness_of :topic
 
   def self.claimed_hash(topic_ids)
     result = {}
diff --git a/spec/models/reviewable_claimed_topic_spec.rb b/spec/models/reviewable_claimed_topic_spec.rb
index e8801e7f13c..c4c54ea2e59 100644
--- a/spec/models/reviewable_claimed_topic_spec.rb
+++ b/spec/models/reviewable_claimed_topic_spec.rb
@@ -4,11 +4,14 @@ require 'rails_helper'
 
 RSpec.describe ReviewableClaimedTopic, type: :model do
 
-  it "ensures uniqueness" do
-    claimed = Fabricate(:reviewable_claimed_topic)
-    expect(-> {
-      ReviewableClaimedTopic.create!(topic_id: claimed.topic_id, user_id: Fabricate(:user).id)
-    }).to raise_error(ActiveRecord::RecordNotUnique)
+  it "respects the uniqueness constraint" do
+    topic = Fabricate(:topic)
+
+    ct = ReviewableClaimedTopic.new(topic_id: topic.id, user_id: Fabricate(:user).id)
+    expect(ct.save).to eq(true)
+
+    ct = ReviewableClaimedTopic.new(topic_id: topic.id, user_id: Fabricate(:user).id)
+    expect(ct.save).to eq(false)
   end
 
 end
diff --git a/spec/requests/reviewable_claimed_topics_controller_spec.rb b/spec/requests/reviewable_claimed_topics_controller_spec.rb
index 134ba396ca4..81dc06e3c73 100644
--- a/spec/requests/reviewable_claimed_topics_controller_spec.rb
+++ b/spec/requests/reviewable_claimed_topics_controller_spec.rb
@@ -33,6 +33,14 @@ describe ReviewableClaimedTopicsController do
         expect(response.code).to eq("200")
         expect(ReviewableClaimedTopic.where(user_id: moderator.id, topic_id: topic.id).exists?).to eq(true)
       end
+
+      it "won't an error if you claim twice" do
+        SiteSetting.reviewable_claiming = 'optional'
+        post "/reviewable_claimed_topics.json", params: params
+        expect(ReviewableClaimedTopic.where(user_id: moderator.id, topic_id: topic.id).exists?).to eq(true)
+        post "/reviewable_claimed_topics.json", params: params
+        expect(response.code).to eq("200")
+      end
     end
   end