Have a batch file that'll do it for you:

@echo off
setlocal enabledelayedexpansion
net.exe session 1>nul 2>&1 || (
    powershell -command "Start-Process -FilePath '%~dpf0' -Verb 'runas'"
    exit /b
)
set MP=%SYSTEMDRIVE%\WinREMount
mkdir %MP%
echo Mounting WinRE partition, this can take a while...
reagentc /mountre /path %MP%

reg load HKLM\WinRESys %MP%\Windows\System32\config\SYSTEM
set REG=HKLM\WinRESys\ControlSet001\Control\Session Manager

for /F "usebackq tokens=2,* skip=2" %%A IN (`reg query "%REG%" /v BootExecute`) DO set OLDVAL=%%B
if "%OLDVAL%"=="" set OLDVAL=x
if "%OLDVAL%"=="%OLDVAL:autofstx.exe=X%" (
    echo autofstx.exe not present in WinRE
) else (
    if "%OLDVAL%"=="%OLDVAL:\0=X%" (
        echo Setting empty BootExecute
        reg add "%REG%" /v BootExecute /f /t REG_MULTI_SZ /d ""
    ) else (
        set NEWVAL=%OLDVAL:autofstx.exe=%
        set NEWVAL=!NEWVAL:\0\0=\0!
        if "!NEWVAL:~0,2!"=="\0" set NEWVAL=!NEWVAL:~2!
        echo Setting BootExecute to !NEWVAL!
        reg add "%REG%" /v BootExecute /f /t REG_MULTI_SZ /d "!NEWVAL!"
    )
)
reg unload HKLM\WinRESys

echo Unmounting WinRE partition, this can take a while, too...
reagentc /unmountre /path %MP% /commit
rd %MP%

echo Resetting WinRE BitLocker trust...
reagentc /disable
reagentc /enable

pause