diff --git a/src/calibre/gui2/book_details.py b/src/calibre/gui2/book_details.py
index 07a963c81b..ebb7c9d5ed 100644
--- a/src/calibre/gui2/book_details.py
+++ b/src/calibre/gui2/book_details.py
@@ -143,6 +143,8 @@ def render_data(mi, use_roman_numbers=True, all_fields=False):
                         vals['author_sort'] = aut.replace(' ', '+')
                     link = formatter.safe_format(
                             gprefs.get('default_author_link'), vals, '', vals)
+                else:
+                    link = ''
                 if link:
                     link = prepare_string_for_xml(link)
                     authors.append(u'<a href="%s">%s</a>'%(link, aut))