Custom keyboard layout switch do not work on lock screen

I have two keyboard layouts enabled on my PC, "English (USA)" and "Russian", they are switched by pressing Alt+Shift.

When I try lock screen and change layout by Alt+Shift the screen freezes for a few seconds, then flashes once, as if the graphics crashed, then reappears, but the layout is not changing.

However, I can change the layout with the mouse, or use a standard shortcut Super+Space.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: unity 7.4.0+16.04.20160715-0ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-31.50-generic 4.4.13
Uname: Linux 4.4.0-31-generic x86_64
.tmp.unity_support_test.0:

ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: compiz
CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0'
CompositorUnredirectFSW: true
CurrentDesktop: Unity
Date: Wed Aug 10 00:14:31 2016
DistUpgraded: Fresh install
DistroCodename: xenial
DistroVariant: ubuntu
GraphicsCard:
 Advanced Micro Devices, Inc. [AMD/ATI] Bonaire XTX [Radeon R7 260X/360] [1002:6658] (prog-if 00 [VGA controller])
   Subsystem: PC Partner Limited / Sapphire Technology Bonaire XTX [Radeon R7 260X/360] [174b:e258]
InstallationDate: Installed on 2016-04-23 (108 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
LightdmDisplayLog: (II) Server terminated successfully (0). Closing log file.
MachineType: To Be Filled By O.E.M. To Be Filled By O.E.M.
ProcKernelCmdLine: BOOT_IMAGE=/@/boot/vmlinuz-4.4.0-31-generic root=UUID=683d2976-4833-4fd9-9f14-1864d4e39bc5 ro rootflags=subvol=@ quiet splash vt.handoff=7
SourcePackage: unity
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 05/12/2015
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: P2.20
dmi.board.name: Z97 Pro4
dmi.board.vendor: ASRock
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: To Be Filled By O.E.M.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrP2.20:bd05/12/2015:svnToBeFilledByO.E.M.:pnToBeFilledByO.E.M.:pvrToBeFilledByO.E.M.:rvnASRock:rnZ97Pro4:rvr:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.name: To Be Filled By O.E.M.
dmi.product.version: To Be Filled By O.E.M.
dmi.sys.vendor: To Be Filled By O.E.M.
upstart.unity-panel-service-lockscreen.log:
 (unity-panel-service:8308): GLib-CRITICAL **: Source ID 4294967295 was not found when attempting to remove it

 (unity-panel-service:8308): GLib-CRITICAL **: Source ID 4294967295 was not found when attempting to remove it

 (unity-panel-service:8367): GLib-CRITICAL **: Source ID 4294967295 was not found when attempting to remove it
version.compiz: compiz 1:0.9.12.2+16.04.20160714-0ubuntu1
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.70+git1607251449.f19cd3a~x~padoka0
version.libgl1-mesa-dri: libgl1-mesa-dri 12.1~git1600803153900.1743c41~x~padoka0
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 12.1~git1600803153900.1743c41~x~padoka0
version.xserver-xorg-core: xserver-xorg-core 2:1.18.3-1ubuntu2.3
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.10.1-1ubuntu2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.7.99+git1607251445.94fe42f~x~padoka0
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git1607311945.49daf5d~x~padoka0
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.12+git1607251455.6473b68~x~padoka0
xserver.bootTime: Wed Aug 10 00:06:28 2016
xserver.configfile: default
xserver.errors:

xserver.logfile: /var/log/Xorg.0.log
xserver.version: 2:1.18.3-1ubuntu2.3
xserver.video_driver: radeon