diff --git a/mercurial/bundle2.py b/mercurial/bundle2.py
--- a/mercurial/bundle2.py
+++ b/mercurial/bundle2.py
@@ -1729,7 +1729,7 @@
     extrakwargs = {}
     targetphase = inpart.params.get('targetphase')
     if targetphase is not None:
-        extrakwargs['targetphase'] = int(targetphase)
+        extrakwargs[r'targetphase'] = int(targetphase)
     ret = _processchangegroup(op, cg, tr, 'bundle2', 'bundle2',
                               expectedtotal=nbchangesets, **extrakwargs)
     if op.reply is not None: