diff --git a/lib/outlook/translations/translation.ex b/lib/outlook/translations/translation.ex
index 2cd972c..225cd1f 100644
--- a/lib/outlook/translations/translation.ex
+++ b/lib/outlook/translations/translation.ex
@@ -26,5 +26,8 @@ defmodule Outlook.Translations.Translation do
     |> cast(attrs, [:lang, :title, :teaser, :date, :public, :unauthorized])
     |> cast(attrs, [:content], force_changes: true)
     |> validate_required([:lang, :title, :teaser, :content, :date, :public, :unauthorized])
+    |> unique_constraint([:lang, :article_id],
+        message: "translation for this language already exists",
+        name: :article_id_lang_unique_index)
   end
 end
diff --git a/priv/repo/migrations/20221230170041_add_lang_article_id_unique_index_to_translations.exs b/priv/repo/migrations/20221230170041_add_lang_article_id_unique_index_to_translations.exs
new file mode 100644
index 0000000..d81ffc4
--- /dev/null
+++ b/priv/repo/migrations/20221230170041_add_lang_article_id_unique_index_to_translations.exs
@@ -0,0 +1,7 @@
+defmodule Outlook.Repo.Migrations.AddLangArticleIdUniqueIndexToTranslations do
+  use Ecto.Migration
+
+  def change do
+    create unique_index(:translations, [:article_id, :lang], name: :article_id_lang_unique_index)
+  end
+end