diff --git a/SharePointFunctions.ps1 b/SharePointFunctions.ps1
index beaffe6..fc17679 100644
--- a/SharePointFunctions.ps1
+++ b/SharePointFunctions.ps1
@@ -483,7 +483,7 @@ function Convert-Files {
                     
                     Write-Host "Saving as XLSX: $xlsxPath"
                     # Save directly to the final path
-                    $workbook.SaveAs([string]$xlsxPath, [Microsoft.Office.Interop.Excel.XlFileFormat]::xlWorkbookDefault)
+                    $workbook.SaveAs([string]$xlsxPath, 51)  # 51 = xlWorkbookDefault (xlsx format)
                     $workbook.Close($true)
                     
                     Start-Sleep -Seconds 2  # Give Excel time to finish