diff --git a/src/calibre/library/caches.py b/src/calibre/library/caches.py
index d577122de8..50af29bb70 100644
--- a/src/calibre/library/caches.py
+++ b/src/calibre/library/caches.py
@@ -150,7 +150,7 @@ def _match(query, value, matchkind):
                 elif query == t:
                     return True
             elif matchkind == REGEXP_MATCH:
-                return re.search(query, icu_lower(t), re.I|re.UNICODE)
+                return re.search(query, t, re.I|re.UNICODE)
             elif matchkind == CONTAINS_MATCH:
                 if pref_use_primary_find_in_search:
                     return primary_find(query, t)[0] != -1