diff --git a/addons/l10n_ch/dta/invoice.py b/addons/l10n_ch/dta/invoice.py
index 40109196b9e..8af850ef6c2 100644
--- a/addons/l10n_ch/dta/invoice.py
+++ b/addons/l10n_ch/dta/invoice.py
@@ -50,10 +50,10 @@ class account_invoice(osv.osv):
 	}
 
 	def _check_bvr(self, cr, uid, ids):
-		return True
+		return False
 	
 	_constraints = [
-		(_check_bvr, 'Error ! Invalid Bvr Number.', [''])
+		(_check_bvr, 'Error : Invalid Bvr Number.', [''])
 	]