diff --git a/sync-skills.ps1 b/sync-skills.ps1
index de6e170..8df0fa3 100644
--- a/sync-skills.ps1
+++ b/sync-skills.ps1
@@ -1,11 +1,17 @@
 [CmdletBinding()]
 param(
     [string] $SourceRoot = 'C:\Users\dkucinski\.scout\m-skills',
-    [string] $RepositoryRoot = $PSScriptRoot
+    [string] $RepositoryRoot
 )
 
 $ErrorActionPreference = 'Stop'
 
+# $PSScriptRoot is empty when the script is launched as `powershell -File <relative path>`
+# (Windows PowerShell 5.1), which would make the Resolve-Path below fail on an empty string.
+if ([string]::IsNullOrWhiteSpace($RepositoryRoot)) {
+    $RepositoryRoot = if ($PSScriptRoot) { $PSScriptRoot } else { Split-Path -Parent $MyInvocation.MyCommand.Path }
+}
+
 $repositoryRoot = (Resolve-Path -LiteralPath $RepositoryRoot).Path
 $sourceRoot = (Resolve-Path -LiteralPath $SourceRoot).Path
 $logDirectory = Join-Path $repositoryRoot 'logs'