pg_shdepend big

Cluster contains only single user database. Database size is 355 MB
All database objects are owned by single role.

I selected bigger tables from database and found that pg_shdepend is big:

First number is table size, second number is table size with index files.

pg_shdepend 9352 kB 18 MB
pg_shdepend_depender_index 7344 kB 7344 kB
pg_shdepend_reference_index 1312 kB 1312 kB
pg_depend_depender_index 1040 kB 1040 kB

Is it normal that pg_shdepend is so big ?

Andrus.