diff -r a8ccd821b7d2 -r ac8cf125d8d5 mercurial/merge.py
--- a/mercurial/merge.py	Mon Feb 04 21:14:37 2019 -0800
+++ b/mercurial/merge.py	Mon Feb 04 21:19:05 2019 -0800
@@ -1506,9 +1506,8 @@
                             conflicting = p
                             break
                 if repo.wvfs.lexists(conflicting):
-                    absf = repo.wjoin(conflicting)
-                    orig = scmutil.origpath(ui, repo, absf)
-                    util.rename(absf, orig)
+                    orig = scmutil.backuppath(ui, repo, conflicting)
+                    util.rename(repo.wjoin(conflicting), orig)
             wctx[f].clearunknown()
             atomictemp = ui.configbool("experimental", "update.atomic-file")
             wctx[f].write(fctx(f).data(), flags, backgroundclose=True,