ERROR: update or delete on table "users" violates foreign key constraint "fk_rails_03de2dc08c" on table "comments"

I am stuck on this error and not able to figure out whats wrong.

rails aborted! ActiveRecord::InvalidForeignKey: PG::ForeignKeyViolation: ERROR: update or delete on table "users" violates foreign key constraint "fk_rails_03de2dc08c" on table "comments" DETAIL: Key (id)=(11) is still referenced from table "comments". : DELETE FROM "users" WHERE "users"."id" = $1 #31