diff --git a/src/calibre/ebooks/metadata/opf2.py b/src/calibre/ebooks/metadata/opf2.py
index 5c2477c3dc..dadca610ae 100644
--- a/src/calibre/ebooks/metadata/opf2.py
+++ b/src/calibre/ebooks/metadata/opf2.py
@@ -529,6 +529,14 @@ class OPF(object): # {{{
         self.find_toc()
         self.read_user_metadata()
 
+    def get_all_user_metadata(self, make_copy):
+        '''
+        return a dict containing all the custom field metadata associated with
+        the book.
+        '''
+        self.read_user_metadata()
+        return self._user_metadata_
+
     def read_user_metadata(self):
         self._user_metadata_ = {}
         temp = Metadata('x', ['x'])