diff --git a/src/calibre/gui2/viewer/highlights.py b/src/calibre/gui2/viewer/highlights.py
index 7702ba146b..8ff9694fbe 100644
--- a/src/calibre/gui2/viewer/highlights.py
+++ b/src/calibre/gui2/viewer/highlights.py
@@ -24,7 +24,7 @@ class Highlights(QListWidget):
 
     def load(self, highlights):
         self.clear()
-        for h in highlights:
+        for h in highlights or ():
             i = QListWidgetItem(h['highlighted_text'], self)
             i.setData(Qt.UserRole, h)