diff --git a/addons/purchase/i18n/purchase.pot b/addons/purchase/i18n/purchase.pot
index 386af71cb22..32ee4c3f3a0 100644
--- a/addons/purchase/i18n/purchase.pot
+++ b/addons/purchase/i18n/purchase.pot
@@ -2398,3 +2398,10 @@ msgid ""
 "Your quotation contains products from company %s whereas your quotation belongs to company %s. \n"
 " Please change the company of your quotation or remove the products from other companies (%s)."
 msgstr ""
+
+
+#. module: purchase
+#: code:addons/purchase/models/purchase.py:0
+#, python-format
+msgid "You cannot change the type of a purchase order line. Instead you should delete the current line and create a new line of the proper type."
+msgstr ""
diff --git a/addons/purchase/models/purchase.py b/addons/purchase/models/purchase.py
index b0d8316f342..d2a43bea5bd 100644
--- a/addons/purchase/models/purchase.py
+++ b/addons/purchase/models/purchase.py
@@ -902,7 +902,7 @@ class PurchaseOrderLine(models.Model):
 
     def write(self, values):
         if 'display_type' in values and self.filtered(lambda line: line.display_type != values.get('display_type')):
-            raise UserError("You cannot change the type of a purchase order line. Instead you should delete the current line and create a new line of the proper type.")
+            raise UserError(_("You cannot change the type of a purchase order line. Instead you should delete the current line and create a new line of the proper type."))
 
         if 'product_qty' in values:
             for line in self: