diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -2287,7 +2287,7 @@ class revlog(object):
     DELTAREUSEALL = {'always', 'samerevs', 'never', 'fulladd'}
 
     def clone(self, tr, destrevlog, addrevisioncb=None,
-              deltareuse=DELTAREUSESAMEREVS, deltabothparents=None):
+              deltareuse=DELTAREUSESAMEREVS, forcedeltabothparents=None):
         """Copy this revlog to another, possibly with format changes.
 
         The destination revlog will contain the same revisions and nodes.
@@ -2321,9 +2321,9 @@ class revlog(object):
         deltas will be recomputed if the delta's parent isn't a parent of the
         revision.
 
-        In addition to the delta policy, the ``deltabothparents`` argument
-        controls whether to compute deltas against both parents for merges.
-        By default, the current default is used.
+        In addition to the delta policy, the ``forcedeltabothparents``
+        argument controls whether to force compute deltas against both parents
+        for merges. By default, the current default is used.
         """
         if deltareuse not in self.DELTAREUSEALL:
             raise ValueError(_('value for deltareuse invalid: %s') % deltareuse)
@@ -2346,7 +2346,7 @@ class revlog(object):
             elif deltareuse == self.DELTAREUSESAMEREVS:
                 destrevlog._lazydeltabase = False
 
-            destrevlog._deltabothparents = deltabothparents or oldamd
+            destrevlog._deltabothparents = forcedeltabothparents or oldamd
 
             populatecachedelta = deltareuse in (self.DELTAREUSEALWAYS,
                                                 self.DELTAREUSESAMEREVS)
diff --git a/mercurial/upgrade.py b/mercurial/upgrade.py
--- a/mercurial/upgrade.py
+++ b/mercurial/upgrade.py
@@ -456,7 +456,7 @@ def _revlogfrompath(repo, path):
         #reverse of "/".join(("data", path + ".i"))
         return filelog.filelog(repo.svfs, path[5:-2])
 
-def _copyrevlogs(ui, srcrepo, dstrepo, tr, deltareuse, deltabothparents):
+def _copyrevlogs(ui, srcrepo, dstrepo, tr, deltareuse, forcedeltabothparents):
     """Copy revlogs between 2 repos."""
     revcount = 0
     srcsize = 0
@@ -578,7 +578,7 @@ def _copyrevlogs(ui, srcrepo, dstrepo, t
         ui.note(_('cloning %d revisions from %s\n') % (len(oldrl), unencoded))
         oldrl.clone(tr, newrl, addrevisioncb=oncopiedrevision,
                     deltareuse=deltareuse,
-                    deltabothparents=deltabothparents)
+                    forcedeltabothparents=forcedeltabothparents)
 
         info = newrl.storageinfo(storedsize=True)
         datasize = info['storedsize'] or 0