diff -r 66dc5a522f37 -r bd5858c28bbe mercurial/revlogutils/flagutil.py
--- a/mercurial/revlogutils/flagutil.py	Wed Sep 04 00:13:45 2019 +0200
+++ b/mercurial/revlogutils/flagutil.py	Wed Sep 04 00:34:03 2019 +0200
@@ -192,7 +192,8 @@
                     if operation == 'raw':
                         vhash = rawtransform(self, text)
                     elif operation == 'read':
-                        text, vhash = readtransform(self, text)
+                        text, vhash, s = readtransform(self, text)
+                        outsidedata.update(s)
                     else: # write operation
                         text, vhash = writetransform(self, text)
                 validatehash = validatehash and vhash