diff --git a/modules/production_outsourcing/message.xml b/modules/production_outsourcing/message.xml
index f625a8f9da..de51cb8c33 100644
--- a/modules/production_outsourcing/message.xml
+++ b/modules/production_outsourcing/message.xml
@@ -4,13 +4,16 @@ this repository contains the full copyright notices and license terms. -->
 <tryton>
     <data grouped="1">
         <record model="ir.message" id="msg_pending_purchase_draft">
-            <field name="text">The productions "%(productions)s" cannot be reset to draft as they have pending purchases.</field>
+            <field name="text">The production "%(productions)s" cannot be reset to draft as it has pending purchases.</field>
+            <field name="text_plural">The productions "%(productions)s" cannot be reset to draft as they have pending purchases.</field>
         </record>
         <record model="ir.message" id="msg_pending_purchase_cancel">
-            <field name="text">The productions "%(productions)s" cannot be cancelled as they have pending purchases.</field>
+            <field name="text">The production "%(productions)s" cannot be cancelled as it has pending purchases.</field>
+            <field name="text_plural">The productions "%(productions)s" cannot be cancelled as they have pending purchases.</field>
         </record>
         <record model="ir.message" id="msg_pending_purchase_done">
-            <field name="text">The productions "%(productions)s" cannot be processed as they have pending purchases.</field>
+            <field name="text">The production "%(productions)s" cannot be processed as it has pending purchases.</field>
+            <field name="text_plural">The productions "%(productions)s" cannot be processed as they have pending purchases.</field>
         </record>
     </data>
 </tryton>
diff --git a/modules/production_outsourcing/production.py b/modules/production_outsourcing/production.py
index a8f837f7b3..4bdb9975b3 100644
--- a/modules/production_outsourcing/production.py
+++ b/modules/production_outsourcing/production.py
@@ -3,7 +3,7 @@
 
 from itertools import groupby
 
-from trytond.i18n import gettext
+from trytond.i18n import ngettext
 from trytond.model import ModelView, Workflow, fields
 from trytond.modules.product import round_price
 from trytond.pool import Pool, PoolMeta
@@ -147,8 +147,9 @@ class Production(metaclass=PoolMeta):
             if Warning.check(warning_name):
                 raise PurchaseWarning(
                     warning_name,
-                    gettext(
+                    ngettext(
                         'production_outsourcing.msg_pending_purchase_draft',
+                        len(pendings),
                         productions=names))
         PurchaseLine.delete(to_delete)
 
@@ -175,8 +176,9 @@ class Production(metaclass=PoolMeta):
             if Warning.check(warning_name):
                 raise PurchaseWarning(
                     warning_name,
-                    gettext(
+                    ngettext(
                         'production_outsourcing.msg_pending_purchase_cancel',
+                        len(pendings),
                         productions=names))
         PurchaseLine.delete(to_delete)
 
@@ -278,6 +280,8 @@ class Production(metaclass=PoolMeta):
             if Warning.check(warning_name):
                 raise PurchaseWarning(
                     warning_name,
-                    gettext('production_outsourcing.msg_pending_purchase_done',
+                    ngettext(
+                        'production_outsourcing.msg_pending_purchase_done',
+                        len(productions),
                         productions=names))
         super().do(productions)