diff --git a/src/calibre/utils/config_base.py b/src/calibre/utils/config_base.py
index a50d0fd153..198c09bfcd 100644
--- a/src/calibre/utils/config_base.py
+++ b/src/calibre/utils/config_base.py
@@ -427,7 +427,9 @@ def _prefs():
                    'accented versions, based on the language you have chosen '
                    'for the calibre interface. For example, in '
                    u' English, searching for n will match ñ and n, but if '
-                   'your language is Spanish it will only match n.'))
+                   'your language is Spanish it will only match n. Note that '
+                   'this is much slower than a simple search on very large '
+                   'libraries.'))
 
     c.add_opt('migrated', default=False, help='For Internal use. Don\'t modify.')
     return c