diff --git a/bookshop/srv/cat-service.js b/bookshop/srv/cat-service.js
index a9c629c0..e6b53a77 100644
--- a/bookshop/srv/cat-service.js
+++ b/bookshop/srv/cat-service.js
@@ -9,7 +9,7 @@ class CatalogService extends cds.ApplicationService { init(){
     const {book,quantity} = req.data
     if (quantity < 1) return req.reject (400,`quantity has to be 1 or more`)
     let {stock} = await SELECT `stock` .from (Books,book)
-    if (quantity > stock) return req.reject (409,`${quantity} exceeds stock for book #${book}`)
+    if (quantity > stock) return req.reject (409, "ORDER_EXCEEDS_STOCK", [quantity, book])
     await UPDATE (Books,book) .with ({ stock: stock -= quantity })
     await this.emit ('OrderedBook', { book, quantity, buyer:req.user.id })
     return { stock }
diff --git a/bookshop/srv/i18n/messages_en.properties b/bookshop/srv/i18n/messages_en.properties
new file mode 100644
index 00000000..c9c2641c
--- /dev/null
+++ b/bookshop/srv/i18n/messages_en.properties
@@ -0,0 +1 @@
+ORDER_EXCEEDS_STOCK={0} exceeds stock for book #{1}
\ No newline at end of file