diff --git a/backend/app/controllers/posts_controller.rb b/backend/app/controllers/posts_controller.rb
index ba15e99..bf54551 100644
--- a/backend/app/controllers/posts_controller.rb
+++ b/backend/app/controllers/posts_controller.rb
@@ -314,7 +314,9 @@ class PostsController < ApplicationController
   def viewed
     return head :unauthorized unless current_user
 
-    current_user.viewed_posts << Post.find(params[:id])
+    UserPostView.create_or_find_by!(
+        user: current_user,
+        post: Post.find(params[:id]))
     head :no_content
   end
 
diff --git a/backend/spec/requests/posts_spec.rb b/backend/spec/requests/posts_spec.rb
index aa5f7c1..ca74978 100644
--- a/backend/spec/requests/posts_spec.rb
+++ b/backend/spec/requests/posts_spec.rb
@@ -2559,6 +2559,21 @@ RSpec.describe 'Posts API', type: :request do
 
       expect(user.reload.viewed?(post_record)).to be(true)
     end
+
+    it '204 and keeps one view on repeated requests' do
+      sign_in_as(user)
+
+      expect {
+        post "/posts/#{ post_record.id }/viewed"
+      }.to change(UserPostView, :count).by(1)
+      expect(response).to have_http_status(:no_content)
+
+      expect {
+        post "/posts/#{ post_record.id }/viewed"
+      }.not_to change(UserPostView, :count)
+      expect(response).to have_http_status(:no_content)
+      expect(user.reload.viewed?(post_record)).to be(true)
+    end
   end
 
   describe 'DELETE /posts/:id/viewed' do