diff --git a/src/calibre/gui2/complete2.py b/src/calibre/gui2/complete2.py
index ca4409679e..e9774b6275 100644
--- a/src/calibre/gui2/complete2.py
+++ b/src/calibre/gui2/complete2.py
@@ -51,6 +51,7 @@ class CompleteModel(QAbstractListModel):  # {{{
         self.sort_func = sort_func
         self.all_items = self.current_items = ()
         self.current_prefix = ''
+        self.use_startswith_search = tweaks['completion_mode'] == 'prefix'
 
     def set_items(self, items):
         if self.strip_completion_entries:
@@ -75,7 +76,7 @@ class CompleteModel(QAbstractListModel):  # {{{
             return
         subset = prefix.startswith(old_prefix)
         universe = self.current_items if subset else self.all_items
-        func = primary_startswith if tweaks['completion_mode'] == 'prefix' else containsq
+        func = primary_startswith if self.use_startswith_search else containsq
         if func is primary_startswith and hierarchy_separator:
             if hierarchy_separator != '.':
                 func = partial(hierarchy_startswith, sep=hierarchy_separator)
@@ -353,6 +354,9 @@ class LineEdit(QLineEdit, LineEditECM):
         self.no_popup = False
 
     # Interface {{{
+    def set_use_startswith_search(self, yes: bool) -> None:
+        self.mcompleter.model().use_startswith_search = yes
+
     def set_sort_func(self, sort_func):
         self.mcompleter.model().sort_func = sort_func
 
diff --git a/src/calibre/gui2/languages.py b/src/calibre/gui2/languages.py
index f859bb2867..b49d448c4d 100644
--- a/src/calibre/gui2/languages.py
+++ b/src/calibre/gui2/languages.py
@@ -30,6 +30,7 @@ class LanguagesEdit(EditWithComplete):
         self._rmap = {lower(v):k for k,v in iteritems(self._lang_map)}
         self.init_langs(db)
         self.item_selected.connect(self.update_recently_used)
+        self.lineEdit().set_use_startswith_search(False)
 
     def init_langs(self, db):
         self.update_items_cache(itervalues(self._lang_map))