diff --git a/htdocs/langs/en_US/bills.lang b/htdocs/langs/en_US/bills.lang
index 5027e56b858..5ed49679e04 100644
--- a/htdocs/langs/en_US/bills.lang
+++ b/htdocs/langs/en_US/bills.lang
@@ -148,6 +148,7 @@ ErrorDiscountAlreadyUsed=Error, discount already used
 ErrorInvoiceAvoirMustBeNegative=Error, correct invoice must have a negative amount
 ErrorInvoiceOfThisTypeMustBePositive=Error, this type of invoice must have a positive amount
 ErrorCantCancelIfReplacementInvoiceNotValidated=Error, can't cancel an invoice that has been replaced by another invoice that is still in draft status
+ErrorThisPartOrAnotherIsAlreadyUsedSoDiscountSerieCantBeRemoved=This part or another is already used so discount serie cant be removed.
 BillFrom=From
 BillTo=To
 ActionsOnBill=Actions on invoice
@@ -519,4 +520,4 @@ CreateOneBillByThird=Create one invoice per third party (otherwise, one invoice
 BillCreated=%s bill(s) created
 StatusOfGeneratedDocuments=Status of document generation
 DoNotGenerateDoc=Do not generate document file
-AutogenerateDoc=Auto generate document file
\ No newline at end of file
+AutogenerateDoc=Auto generate document file