diff --git a/controllers/main.py b/controllers/main.py
index 4165650cd0cff0006249e387db402e099ded0f20..f9d60b6346442c223dce9349ebc2b5cea3062bed 100644
--- a/controllers/main.py
+++ b/controllers/main.py
@@ -203,9 +203,12 @@ class ExportJournalCg(http.Controller):
             return line.debit
 
     def _get_partner_number(self, partner):
-        number = partner.member_number + '00'
-        prefix = 8 - len(number)
-        return (prefix * '0') + number
+        if partner.member_number:
+            number = partner.member_number + '00'
+            prefix = 8 - len(number)
+            return (prefix * '0') + number
+        else:
+            return ""
 
     def export_cg_csv(self, lines_to_export, filename_):
         fp = StringIO()