diff --git a/l10n_es_aeat/wizard/export_to_boe.py b/l10n_es_aeat/wizard/export_to_boe.py
index f2a5d1cb8d7..b1bd4718601 100644
--- a/l10n_es_aeat/wizard/export_to_boe.py
+++ b/l10n_es_aeat/wizard/export_to_boe.py
@@ -56,7 +56,7 @@ def _formatString(self, text, length, fill=' ', align='<'):
             return fill * length
         # Replace accents and convert to upper
         from unidecode import unidecode
-        text = unicode(text.upper())
+        text = unicode(text).upper()
         text = ''.join([unidecode(x) if x not in (u'Ñ', u'Ç') else x
                         for x in text])
         text = re.sub(