diff --git a/ddportfolioservice/model/urlbuilder.py b/ddportfolioservice/model/urlbuilder.py
index 7b001fd..462f241 100644
--- a/ddportfolioservice/model/urlbuilder.py
+++ b/ddportfolioservice/model/urlbuilder.py
@@ -71,7 +71,11 @@ def build_urls(fields):
                              my_config.get(section, url + '.pattern',
                                            False, qfields)])
                     except InterpolationMissingOptionError, e:
-                        data.append(['error', section, url,
-                                     _('Missing input: %s') % \
-                                         _(_FIELDNAMES_MAP[e.reference])])
+                        if e.reference in _FIELDNAMES_MAP:
+                            data.append(['error', section, url,
+                                         _('Missing input: %s') % \
+                                             _(_FIELDNAMES_MAP[e.reference])])
+                        else:
+                            data.append(['error', section, url,
+                                         _('Missing input: %s') % e.reference])
     return data