diff --git a/src/calibre/gui2/viewer/search.py b/src/calibre/gui2/viewer/search.py
index 089e3b7d86..7a2e2acdb3 100644
--- a/src/calibre/gui2/viewer/search.py
+++ b/src/calibre/gui2/viewer/search.py
@@ -332,6 +332,7 @@ class SearchInput(QWidget):  # {{{
         sb.initialize('viewer-{}-panel-expression'.format(panel_name))
         sb.item_selected.connect(self.saved_search_selected)
         sb.history_saved.connect(self.history_saved)
+        sb.history_cleared.connect(self.history_cleared)
         sb.cleared.connect(self.cleared)
         sb.lineEdit().returnPressed.connect(self.find_next)
         h.addWidget(sb)
@@ -388,6 +389,9 @@ class SearchInput(QWidget):  # {{{
             sss = {k: v for k, v in iteritems(sss) if k in history}
             vprefs['saved-{}-settings'.format(self.panel_name)] = sss
 
+    def history_cleared(self):
+        vprefs['saved-{}-settings'.format(self.panel_name)] = {}
+
     def save_search_type(self):
         text = self.search_box.currentText()
         if text and not self.ignore_search_type_changes:
diff --git a/src/calibre/gui2/viewer/widgets.py b/src/calibre/gui2/viewer/widgets.py
index 3751a1cb9d..ce5a354b9d 100644
--- a/src/calibre/gui2/viewer/widgets.py
+++ b/src/calibre/gui2/viewer/widgets.py
@@ -112,6 +112,7 @@ class ResultsDelegate(QStyledItemDelegate):  # {{{
 class SearchBox(HistoryComboBox):  # {{{
 
     history_saved = pyqtSignal(object, object)
+    history_cleared = pyqtSignal()
     cleared = pyqtSignal()
 
     def __init__(self, parent=None):
@@ -127,6 +128,10 @@ class SearchBox(HistoryComboBox):  # {{{
         self.history_saved.emit(self.text(), self.history)
         return ret
 
+    def clear_history(self):
+        super().clear_history()
+        self.history_cleared.emit()
+
     def contextMenuEvent(self, event):
         menu = self.lineEdit().createStandardContextMenu()
         menu.addSeparator()