diff --git a/src/calibre/gui2/viewer/highlights.py b/src/calibre/gui2/viewer/highlights.py
index 5848f4c6f2..b0d223549f 100644
--- a/src/calibre/gui2/viewer/highlights.py
+++ b/src/calibre/gui2/viewer/highlights.py
@@ -356,7 +356,7 @@ class Highlights(QTreeWidget):
                 for key in keys:
                     section = smap[key]
                     if section['tfam']:
-                        section['title'] = ' ➤ '.join(tfam)
+                        section['title'] = ' ➤ '.join(section['tfam'])
                     elif section['tsec'] and section['lsec']:
                         section['title'] = ' ➤ '.join((section['tsec'], section['lsec']))