diff --git a/mercurial/bundle2.py b/mercurial/bundle2.py
--- a/mercurial/bundle2.py
+++ b/mercurial/bundle2.py
@@ -1883,7 +1883,7 @@
 def bundle2getvars(op, part):
     '''unbundle a bundle2 containing shellvars on the server'''
     # An option to disable unbundling on server-side for security reasons
-    if op.ui.configbool('push', 'pushvars.server', False):
+    if op.ui.configbool('push', 'pushvars.server'):
         hookargs = {}
         for key, value in part.advisoryparams:
             key = key.upper()
diff --git a/mercurial/configitems.py b/mercurial/configitems.py
--- a/mercurial/configitems.py
+++ b/mercurial/configitems.py
@@ -361,6 +361,9 @@
 coreconfigitem('progress', 'width',
     default=dynamicdefault,
 )
+coreconfigitem('push', 'pushvars.server',
+    default=False,
+)
 coreconfigitem('server', 'bundle1',
     default=True,
 )