diff --git a/mercurial/merge.py b/mercurial/merge.py
--- a/mercurial/merge.py
+++ b/mercurial/merge.py
@@ -806,6 +806,7 @@
         pa not in ([wctx, p2] + wctx.parents())
         and not forcefulldiff
         and scmutil.istreemanifest(repo)
+        and repo.ui.configbool(b'experimental', b'merge-track-undeleted')
     ):
         # Identify which files are relevant to the merge, so we can limit the
         # total m1-vs-m2 diff to just those files. This has significant