diff --git a/src/calibre/library/database2.py b/src/calibre/library/database2.py
index 4b6fb2f7f2..3b7efd500d 100644
--- a/src/calibre/library/database2.py
+++ b/src/calibre/library/database2.py
@@ -144,6 +144,7 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
         self.initialize_dynamic()
 
     def initialize_dynamic(self):
+        self.field_metadata = FieldMetadata() #Ensure we start with a clean copy
         self.prefs = DBPrefs(self)
         defs = self.prefs.defaults
         defs['gui_restriction'] = defs['cs_restriction'] = ''
@@ -2151,8 +2152,6 @@ books_series_link      feeds
             os.remove(self.dbpath)
             shutil.copyfile(dest, self.dbpath)
             self.connect()
-            self.field_metadata.remove_dynamic_categories()
-            self.field_metadata.remove_custom_fields()
             self.initialize_dynamic()
             self.refresh()
         if os.path.exists(dest):
diff --git a/src/calibre/library/field_metadata.py b/src/calibre/library/field_metadata.py
index e28b6d422a..09dd024b66 100644
--- a/src/calibre/library/field_metadata.py
+++ b/src/calibre/library/field_metadata.py
@@ -306,7 +306,7 @@ class FieldMetadata(dict):
             self._tb_cats[k]['label'] = k
             self._tb_cats[k]['display'] = {}
             self._tb_cats[k]['is_editable'] = True
-            self._add_search_terms_to_map(k, self._tb_cats[k]['search_terms'])
+            self._add_search_terms_to_map(k, v['search_terms'])
         self.custom_field_prefix = '#'
         self.get = self._tb_cats.get
 
@@ -408,16 +408,6 @@ class FieldMetadata(dict):
             self._add_search_terms_to_map(key, [key])
             self.custom_label_to_key_map[label+'_index'] = key
 
-    def remove_custom_fields(self):
-        for key in self.get_custom_fields():
-            del self._tb_cats[key]
-
-    def remove_dynamic_categories(self):
-        for key in list(self._tb_cats.keys()):
-            val = self._tb_cats[key]
-            if val['is_category'] and val['kind'] in ('user', 'search'):
-                del self._tb_cats[key]
-
     def cc_series_index_column_for(self, key):
         return self._tb_cats[key]['rec_index'] + 1