diff -r f82d2d4e71db -r 2f290136b7d6 mercurial/subrepo.py
--- a/mercurial/subrepo.py	Fri Jan 17 21:22:23 2020 +0300
+++ b/mercurial/subrepo.py	Fri Jan 24 15:28:37 2020 -0800
@@ -806,7 +806,7 @@
                 self.ui.debug(
                     b'merging subrepository "%s"\n' % subrelpath(self)
                 )
-                hg.merge(self._repo, state[1], remind=False)
+                hg.merge(dst, remind=False)
 
         wctx = self._repo[None]
         if self.dirty():