pg_dump out of memory for large table with LOB

I am running PostgreSQL 9.6.5 on x86_64-pc-mingw64, compiled by gcc.exe (Rev5, Built by MSYS2 project) 4.9.2, 64-bit
on win2012 with 12Gb RAM
The dumped table is 0.5TB, 17 million rows and LOB uses about 99% of the space.
The pg_dump consumes the entire system memory and swap, then terminates with out of memory error
Is it a bug or normal behavior?
If I do not include LOB in the dump, it works fine.

Here is the dump output:
C:\Users\Administrator> pg_dump -h localhost -Fc -a -b -t signatures -v > d:\postgresql\sig.dmp
pg_dump: last built-in OID is 16383
...
pg_dump: reading row security enabled for table "ibisl1.signatures"
pg_dump: reading policies for table "ibisl1.signatures"
pg_dump: reading large objects
pg_dump: reading dependency data
pg_dump: saving encoding = UTF8
pg_dump: saving standard_conforming_strings = on
out of memory

Jean-Marc Lessard
Administrateur de base de donn?es / Database Administrator
Ultra Electronics Forensic Technology Inc.
T +1 514 489 4247 x4164
www.ultra-forensictechnology.com<http://www.ultra-forensictechnology.com>