--- a/mercurial/revlog.py	Wed Sep 04 03:20:55 2019 +0200
+++ b/mercurial/revlog.py	Tue Sep 03 23:45:38 2019 +0200
@@ -1865,6 +1865,8 @@
             raise error.ProgrammingError(
                 _("trying to add sidedata to a revlog who don't support them")
                 )
+        else:
+            flags |= REVIDX_SIDEDATA
 
         if flags:
             node = node or self.hash(text, p1, p2)