ERROR: operator class "gin__int_ops" does not exist for access method "gin"

[Julie Nishimura]

We migrated some tables from 8.3 postgresql to 9.4, and when I compared tables 
DDL between environments, I've noticed some indices are missing (majority of 
them are using GIN

When I am taking 8.3 ddl for it:
  CREATE INDEX serp_test2
  ON serp_test
  USING gin
  (domainids gin__int_ops);

it gives me error:
ERROR:  operator class "gin__int_ops" does not exist for access method "gin"

Is it possible to retrieve the ddl for operator class and recreate it on 9.4? 
If not, is there any work-around?

Thank you