diff --git a/scripts/deploy-ftp.ps1 b/scripts/deploy-ftp.ps1
index fc554c4..0104a80 100644
--- a/scripts/deploy-ftp.ps1
+++ b/scripts/deploy-ftp.ps1
@@ -47,19 +47,21 @@ function Assert-Tool {
 Assert-Tool "dotnet"
 Assert-Tool $WinScpPath
 
-function Read-PlainOrPrompt([string]$Value, [string]$Prompt, [switch]$Secure) {
+function Read-PlainOrPrompt([string]$Value, [string]$Prompt, [bool]$Secure = $false) {
     if ($Value) { return $Value }
     if ($Secure) {
         $secure = Read-Host -Prompt $Prompt -AsSecureString
-        return [Runtime.InteropServices.Marshal]::PtrToStringUni(
-            [Runtime.InteropServices.Marshal]::SecureStringToBSTR($secure)
-        )
+        $ptr = [Runtime.InteropServices.Marshal]::SecureStringToBSTR($secure)
+        try { return [Runtime.InteropServices.Marshal]::PtrToStringUni($ptr) }
+        finally {
+            if ($ptr -ne [IntPtr]::Zero) { [Runtime.InteropServices.Marshal]::ZeroFreeBSTR($ptr) }
+        }
     }
     return Read-Host -Prompt $Prompt
 }
 
-$FtpPassword         = Read-PlainOrPrompt $FtpPassword "FTP password" -Secure
-$WinRmCredentialPass = Read-PlainOrPrompt $WinRmCredentialPass "WinRM password" -Secure
+$FtpPassword         = Read-PlainOrPrompt $FtpPassword "FTP password" $true
+$WinRmCredentialPass = Read-PlainOrPrompt $WinRmCredentialPass "WinRM password" $true
 
 Write-Host "1) Publishing..." -ForegroundColor Cyan
 New-Item -ItemType Directory -Force -Path $PublishDir | Out-Null