vacuumdb fails with error pg_statistic_relid_att_inh_index constraint violation after upgrade to 9.6

[Swapnil Vaze <swapvaze28@xxxxxxxxx>]

Hello,

We have upgraded our database from 9.5 to 9.6 version. 
After upgrade we ran vacuumdb command and we are getting following error:

vacuumdb: vacuuming of database "advdfat" failed: ERROR:  duplicate key value violates unique constraint "pg_statistic_relid_att_inh_index"

DETAIL:  Key (starelid, staattnum, stainherit)=(1259, 1, f) already exists.

Can anyone help here?

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Thanks & Regards,

Swapnil Vaze