Wrong .po header after update from 2.7 to 2.9

[CSharpRU]

Steps to reproduce:

Create new language and add it to some project.

Results (Expected/Actual):

Actual:

"Project-Id-Version: PACKAGE VERSION\n"
"Report-Msgid-Bugs-To: \n"
"POT-Creation-Date: 2017-09-27 09:50+0200\n"
"PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
"Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
"Language-Team: LANGUAGE <[email protected]>\n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"
"X-Generator: Translate Toolkit 2.2.5\n"

Expected:

"Project-Id-Version: PACKAGE VERSION\n"
"Report-Msgid-Bugs-To: \n"
"POT-Creation-Date: 2017-09-27 09:50+0200\n"
"PO-Revision-Date: 2016-11-21 07:00+0200\n"
"Last-Translator: Translator <translator@pootle>\n"
"Language-Team: LANGUAGE <[email protected]>\n"
"Language: uk_UA\n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"
"Plural-Forms: nplurals=3; plural=(n%10==1 && n%100!=11 ? 0 : n%10>=2 && "
"n%10<=4 && (n%100<10 || n%100>=20) ? 1 : 2);\n"
"X-Generator: Pootle 2.9\n"
"X-POOTLE-MTIME: 1479711623.773717\n"

Environment (i.e. 'pootle --version', DB, OS, Browser):

Pootle 2.9.0rc1 [9545ab6] (Django 1.10.8, Translate Toolkit 2.2.5)
psql (PostgreSQL) 9.5.6

Getting ModuleBuildError: Module build failed: Error: No Language header found! with webpack due to wrong header.