diff --git a/windows/installer/build.ps1 b/windows/installer/build.ps1
index 7a6e78d..6208a27 100644
--- a/windows/installer/build.ps1
+++ b/windows/installer/build.ps1
@@ -96,14 +96,18 @@ function Invoke-ForceLegacySetup {
     if (-not (Test-Path $bootwim)) { throw "boot.wim not found: $bootwim" }
     Mount-WindowsImage -ImagePath $bootwim -Index 2 -Path $bootmnt | Out-Null
     try {
-        $cmdline = 'X:\sources\setup.exe'
-        if (-not (Test-Path (Join-Path $bootmnt 'sources\setup.exe')) -and
-                  (Test-Path (Join-Path $bootmnt 'setup.exe'))) { $cmdline = 'X:\setup.exe' }
+        # Inject the answer file into the WinPE image at a fixed X: path, and launch
+        # legacy setup with an EXPLICIT /unattend -- the implicit media search is
+        # unreliable when setup is launched via the CmdLine override (legacy Setup
+        # otherwise still shows the language page).
+        Copy-Item (Join-Path $PSScriptRoot 'autounattend\autounattend.xml') (Join-Path $bootmnt 'autounattend.xml') -Force
+        $setup = if (Test-Path (Join-Path $bootmnt 'sources\setup.exe')) { 'X:\sources\setup.exe' } else { 'X:\setup.exe' }
+        $cmdline = "$setup /unattend:X:\autounattend.xml"
         $hive = Join-Path $bootmnt 'Windows\System32\config\SYSTEM'
         & reg load 'HKLM\SM_BOOT' $hive | Out-Null
         try {
             & reg add 'HKLM\SM_BOOT\Setup' /v CmdLine /t REG_SZ /d $cmdline /f | Out-Null
-            Write-Host "   WinPE Setup\CmdLine = $cmdline (legacy Setup forced)"
+            Write-Host "   WinPE Setup\CmdLine = $cmdline (legacy Setup + explicit unattend)"
         } finally {
             [gc]::Collect(); Start-Sleep -Seconds 2
             & reg unload 'HKLM\SM_BOOT' | Out-Null