Except for NSIS' '/D' arg

lib/core.ps1

@@ -600,8 +600,7 @@ function Invoke-ExternalCommand {
     [CmdletBinding(DefaultParameterSetName = "Default")]
     [OutputType([Boolean])]
     param (
-        [Parameter(Mandatory = $true,
-                   Position = 0)]
+        [Parameter(Mandatory = $true, Position = 0)]
         [Alias("Path")]
         [ValidateNotNullOrEmpty()]
         [String]
@@ -664,9 +663,9 @@ function Invoke-ExternalCommand {
             $escapedArgs = $ArgumentList | ForEach-Object {
                 # escape N consecutive backslash(es), which are followed by a double quote or at the end of the string, to 2N consecutive ones
                 $s = $_ -replace '(\\+)(""|$)', '$1$1$2'
-                # quote the path if it contains spaces
-                if ($s -match ' ') {
-                    $s = $s -replace '([A-Za-z]:[\\/].*)', '`"$1`"'
+                # quote the path if it contains spaces and is not NSIS's '/D' argument
+                if ($s -match ' ' -and $s -notmatch '/D=[A-Z]:[\\/].*') {
+                    $s = $s -replace '([A-Z]:[\\/].*)', '`"$1`"'
                 } else {
                     $s
                 }