pg_upgrade from 9.5.10 to 12 fails with encoding issue

I am trying to upgrade a cluster of version 9.5.19 to version 12.1 but seems like upgrade is getting failed because of database encoding issue, I am getting below error while running pg_upgrade command with -c 

"lc_collate values for database "postgres" do not match:  old "en_US.UTF-8", new "C.UTF-8" Failure, exiting", 

I have tried to create new cluster f version 12 using initdb --encoding parameter but it create encoding as C.UTF-8 only and old cluster is with encoding en_us_UTF-8.

Kindly assist to resolve this issue.

Thanks and regards