diff --git a/source/app/controllers/util.py b/source/app/controllers/util.py
index 1b10fc0..f3d582f 100644
--- a/source/app/controllers/util.py
+++ b/source/app/controllers/util.py
@@ -1455,7 +1455,7 @@ def _comprobante(doc, options):
     serie = ''
     if 'serie' in data:
         serie = '{} -'.format(data['serie'])
-    data['seriefolio'] = '{}{}'.format(serie, data['folio'])
+    data['seriefolio'] = '{}{}'.format(serie, data.get('folio', ''))
     data['totalenletras'] = to_letters(float(data['total']), data['moneda'])
 
     is_nomina = options.get('is_nomina', False)