V12 update error

frappe@instance-1:~/frappe-bench$ bench switch-to-branch version-12
Branch version-12 does not exist in Upstream for erpnext
Branch version-12 does not exist in Upstream for bench_manager
Traceback (most recent call last):
File “/usr/local/bin/bench”, line 11, in
load_entry_point(‘bench’, ‘console_scripts’, ‘bench’)()
File “/home/frappe/.bench/bench/cli.py”, line 40, in cli
bench_command()
File “/usr/local/lib/python2.7/dist-packages/click/core.py”, line 764, in call
return self.main(*args, **kwargs)
File “/usr/local/lib/python2.7/dist-packages/click/core.py”, line 717, in main
rv = self.invoke(ctx)
File “/usr/local/lib/python2.7/dist-packages/click/core.py”, line 1137, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File “/usr/local/lib/python2.7/dist-packages/click/core.py”, line 956, in invoke
return ctx.invoke(self.callback, **ctx.params)
File “/usr/local/lib/python2.7/dist-packages/click/core.py”, line 555, in invoke
return callback(*args, **kwargs)
File “/home/frappe/.bench/bench/commands/update.py”, line 138, in switch_to_branch
switch_to_branch(branch=branch, apps=list(apps), upgrade=upgrade)
File “/home/frappe/.bench/bench/app.py”, line 397, in switch_to_branch
switch_branch(branch, apps=apps, bench_path=bench_path, upgrade=upgrade)
File “/home/frappe/.bench/bench/app.py”, line 363, in switch_branch
raise MajorVersionUpgradeException(“Switching to {0} will cause upgrade from {1} to {2}. Pass --upgrade to confirm”.format(branch, version_upgrade[1], version_upgrade[2]), version_upgrade[1], version_upgrade[2])
bench.app.MajorVersionUpgradeException: Switching to version-12 will cause upgrade from 11 to 12. Pass --upgrade to confirm
frappe@instance-1:~/frappe-bench$